And Pawsplay, what else do you have in mind?
Planetary romance / gonzo swords-and-sorcery stuff would be welcome. Great for pulp-inspired games or cross-genre stuff. There is an aesthetic that started in the 1930s that went through about the early 1960s that combined various elements of nudity, tunic-wearing, anachronism, and just oddness that I find very resonant. You can see a little even in Flash Gordon or some of the weirder original Star Trek Episodes, but you really see this on vintage covers of old cheap paperbacks.
Science fantasy. Even within one setting, such as Planescape, Spelljammer, Dragonstar, Final Fantasy type settings, Tekumel, Dying Earth, Thundarr the Barbarian, Castle in the Sky, Escaflowne and so forth, there is usually such a wide variety of aesthetics I think it's almost certain I would find something useful. Characters can be cobbled from fantasy or modern sources, but ships, cityscapes, and the like would be different. The idea is to combine technological lines and obvious steel, rubber, and powerful energy sources with fanciful aesthetics, anachronistic elements such as sailing ships with obvious technological components, and fanciful elements like flying castles.
Supers. Fight scenes, giant computers, space scenes, city scapes, monsters, action poses, squadron poses. I prefer an early Bronze Age style, late 1980s DC stuff mostly plus McFarlane's work on Spider-Man, but I'm not religious about it and I don't think most supers fans are, either. For stock art, line art is best, and the license should allow coloration and alteration, for instance, if I wanted to use the art to represent an NPC.