On a black jade altar lay Yasmela

The army of Thugra Khotan has been defeated and has fled the battlefield taking Princess Yasmela with his. CONAN finds them both in an ancient ruin.

On a black jade altar lay Yasmela, her naked body gleaming like ivory in the weird light. Her garments lay strewn on the floor, as if ripped from her in brutal haste.

From "Black Colossus"
Page 132. The Complete Chronicles of CONAN.

I've found a few examples of pale women of dark altars... they were probably all "supple" as well, a few more to follow.

Naked girls and altars...

After the near extinction of the two peoples battling within the ancient city of Xuchotl, Valeria is taken prisoner by an evil witch who wants to sacrifice her and drain her vitality to sustain her own youth.

On the altar lay Valeria, stark naked, her white flesh gleaming in shocking contrast to the glistening ebon stone. She was not bound. She lay at full length, her arms stretched out above her head to their fullest extent. At the head of the altar knelt a young man, holding her wrists firmly. A young woman knelt at the other end of the altar, grasping her ankles. Between them she could neither rise nor move.

From "Red Nails"
Page 569. The Complete Chronicles of CONAN.

Villains, with naked slave-boys...

CONAN is taken prisoner through a combination of ambush, deception and sorcery. He is brought before his gloating, enemies, Tsotha the evil sorcerer, and the  silk wearing, divan lounging Kings, Strabonus and Amalrus.

In front of him stood Tsotha, and on divans lounged Strabonus and Amalrus in their silks and golds, gleaming with jewels, naked slave-boys beside them pouring wine into cups carved of a single sapphire.

From "The Scarlet Citadel"
Page 49. "The Complete Chronicles of CONAN"

So far in,(About 500 pages) this reference to "naked slave-boys" is the only reference to imply homosexual activity that I've picked up on. There was some lesbian S. and M, but references to homosexuality, other than the subtle one here seem pretty much non-existent so far*.

I think this an instance that brings home how long ago the stories were written, when you read an implication of homosexuality being used to emphasise negative traits in the villains.
 

*Obviously I'm not counting the unavoidable homoerotic aspects of a series of books based entirely on the adventures of a largely shirtless, sun tanned guy that works out a lot! :-)

CONAN has lost his lady friend in a dungeon below an ancient city...

CONAN has lost his lady friend, Natala, in a dungeon below an ancient city. Thalis, who is competing with Natala for CONAN's attention, overpowers her and gets a bit lesbo-sadomasochistic on her arse!

As in a nightmare Natala felt her tunic being stripped from her, and the next instant Thalis had jerked up her wrists and bound them barely touching the floor. Twisting her head, Natala saw Thalis unhook a jewel-handed whip from where it hung on the wall, near the ring. The lashes consisted of seven round silk cords, harder yet more pliant than leather thongs.
With a hiss of vindictive gratification, Thalis  drew back her arm, and Natala shrieked as the cords curled across her loins. The tortured girl writhed, and tore agonizedly at the thongs which imprisoned her wrists.
...She had never guessed the punishing power of hard-woven silk cords. Their caress was more exquisitely painful than any birch twig or leather thongs.

From, "The Slithering Shadow"
Page 151-2 "The Complete Chronicles of CONAN"

It's quite interesting that although there have been many instances of cruelty by men upon women being mentioned, the only graphic description I have found so far decribes a woman taking pleasure in cruelty to another woman.