In terms of iconic pieces of artwork they don't come more iconic then this piece of artwork in the Fiend Folio for me. For hours I just stare at it wondering about circumstances that led to this nasty confrontation between the fighter & the lizard men.

This piece of artwork screams 'Sorcery & Planet' to me. What I'm really thinking about is monsters or specifically Dungeons & Dragons or Advanced Dungeons & Dragons first edition monsters that could be put in a 'Sorcery & Planetary' adventure campaign. I was really diving deep into Bill Willingham's artwork from the early Dungeons & Dragons B/X rule books.

And I've been specifically doing a lot of thinking about undead. Specifically wraiths or the more 3.5 advanced versions of these undead horrors the 'dread wraiths'. Why?! Because what happens to the kings & royals of these various wasteland 'Sword & Planet' settings? These ancient kings & queens are not going to go quietly into the sunsets of their empires & reading through some of the D20 Hypertext bears this out;"The oldest and most malevolent wraiths lurk in the depths of forgotten temples and other forsaken places. They can sense the approach of living creatures, and hunger for them. Despite its size, the dread wraith possesses unearthly quickness, and makes use of its Spring Attack feat and natural reach to strike with deadly effect and melt back into the shadows—or the walls." Truly it seems like there should be tons of undead haunting these various desert landscapes in various old school or OSR product. Dark Sun made quite the effect of their undead. But I'm thinking of a Mars filled with various classic unead. This brings to mind Frank Frazetta's 1972 Norseman artwork. The print is available through the Frazetta girls site here. The artwork is used without permission. But as inspiration for these undead kings hungering for the life force of the living.
"Under the dread & alien sky the moons carved their way through the skies like some cancer rotting its way through the cells of reality. The party of adventurers more like a band of cut purses & bandits really had been assembled from the local meeting points of the guild. They were temporary players in a game of robbery & misadventure whose survivors might be come a part of Vartain's Brigand if they were lucky. The abbey was less then fifty years old & had not survived the 'star plague'. The mummified remains of the occupants were still in the places they'd been. Vartain had heard the tale in a nameless desert brothel in the back end of a bed from one of the abbey's last victims. The strange whirled patterns of scars & scabs still sent shutters up the back of Vartain. The female thief was lucky to have made it out of the old pile alive while the rest of her party had joined the monks in their unnatural rest. She fled west into the desert to seek out the sacred prostitute healers of Mruai the miracle workers she once called sisters. Those she once saught to escape might save her life & they did but the spirit of the once proud thief & performer was broken'
'Thama The Twisting Acrobat' had been Vartain's right hand thief & performer for over two years. But this pile had broken her & her brave compatriots. Vartain had only picked the worst scum & murderers he'd found scrapping the gutters for this job. His party made it fifty feet into the door when the first of the blackness just outside of the torch light began to move. Vartain had a score to settle with the alien dead of this place on behalf of his former apprentice & settle it he would! "
Vartain noticed the shadows not fifty feet into the door of the pile moved unnaturally slithering & tittering to themselves. He pulled a bit on his own five ways enchanted sword the product of twisting holy magick & the pulled start light of alien stars of other places best not thought of.
"There
is certainly a world beyond our normal consciousness from which neither
space nor time divides us, but only the barrier of our
sense-perceptions.... this threshold is not immovable. ~William F.
Barrett, On the Threshold of the Unseen, 1918"
There are places best not thought of that sane men do not seek where the touch of the occult & unnatural has created ancient horrors beyond the ken of men. These are things that make a mockery out of the scared thing we call life. They seem like our loved ones, brothers, sisters, lovers, & even strangers but they are of a different order entirely. In the lonely & forgotten places these horrors lurk. They hunger for the energies & vitality of life but their existence is nothing but a blackness into the yawning abyss of inky blackness that not even God or the lesser gods of mankind acknowledge. But they are there in the dungeons, ruins, & deserted places waiting for us to come.
"Yesterday, upon the stair,
I met a man who wasn't there.
He wasn't there again today,
I wish, I wish he'd go away.
When I came home last night at three,
The man was waiting there for me
But when I looked around the hall,
I couldn't see him there at all!"
~Hughes Mearns (1875–1965), "Antigonish," Psyco-ed, c.1899
These things are evil incarnate dripping with the piping cold unnatural hunger of the 'Other place' & suffused with the dark negative energies of the alien undeath. 
1d12 Random Sword & Sorcery Encounters With Alien Wraiths & Their Kind
- This hooded figure is clad in the inky blackness of weird robes that aren't there but surrounding the cold dead flesh are torture marks from Orcs who used him or it for target practice & torture. He sneaks others to share his torture but a nearby Jade talisman will put him to rest for thirty days.
- This strange creeping monstrous wraith seeks company to warm itself from the numbing cold of the all consuming hunger. It is barely humanoid & is bound to a +1 dagger attached to it's shroud.
- Weird cold lights make up this creature that is actually one wraith divided into 1d8 parts of a creature of all consuming hunger. The monster will surround any PC whose name begins with the letter 'A' unless he or she can complete its strange song.
- A dangerous hooded being wearing a space officer's uniform prances back & forth along its predetermined route each night. It will ask for the pass word in common & will attack with full force.The pass word is writ in crayon in the hall in Goblinoid.
- Sitting on a shelf is a glass of what seems like black liquid but is actually an alien wraith drained dry of its soul eons ago. The thing will attack unless an empty wine bottle is placed on the shelf. There are local legends about this monster as it guards 1d6 jade statues.
- An ancient manikin like statue made of a straw like material stands watch over the bones of some ancient creature. From them will pour the inky blackness of this wraith. The monster hungers for the soul of any murderers present. It will ask questions & apologize even as it drains the PC's dry. There are six pieces of alien silver dollars nearby that can drive this horror back to its hiding place. But it will come back twice as strong.
- Twelve black rods float in the air around this place & are actually the soul of this wraith. This thing hates the living & will kill anyone trying to pass through it. Only a song of its kind will banish this thing back to the 'Other place'. There are seven hundred & seventy mathematical formula that it whispers to itself in its hungry madness.
- Seven black hands make up this wraith & they flutter around this place like moths. The non sound of their passing is strange & sense of cold as well as danger hangs here. They will try & seize anyone coming into their place. There upon one wall is a song that can be played to freeze these horrors in place for 1d10 rounds.
- Seven black swords wielded by a black ebony humanoid figure make up this wraith. The thing will form in 2 rounds & attack.
- There are ten stick figures that form into an alien inky humanoid spider like being. It will spout poetry that reveals the treasure it sought in common & its location as it drains the PCs.
- Six strange crow like inky blobs make up this wraith & will mock the PC's with insults & alien slurs laughing like a maniac all the while. This thing knows the location of the ten treasures of this dungeon & will only reveal them after murdering a human. Of course it will cleverly try to double or triple cross the party.
- This inky being resembles a monk or priest & will appear to be helpless. It will try to lure the PC's into helping it. The thing lives in a burnt out old iron lantern that hovers mystically in a corner of this place. Destroy the lamp & destroy the wraith. Did I mention the treasure map in the false bottom of the lamp?!