||May I add my suggestions?
Creatures/characters: golem, warden, guard, hermit, skeleton, figure in a door, plant, robot
Locations: sanctuary, prison, dungeon, fortress, hall
Details: you can just paint the gate keeper posing in front of his gate or fighting with intruders. But the gate keeper may be a creature like the Sphinx and his riddle, who would grant free access if your answer correctly. He may be gigantic, he may be tiny, he may be numerous, he may feed on intruders as well.
Creatures/Characters: crazy steampunk guy, robot, tentacle alien, military mechanic
Locations: warehouse, garage, workshop
Details: in team or alone, he will probably look dirty if he is not alien. In a general way, the place where he works is a mess, with his tools scatters everywhere, junks littering the ground. He may be a she, and she could be ugly or gorgeous. A wrench is a good accessory, and leather will probably will be his favorite fabric. If alien, he may be hovering. It may be just a robotic facility.
Creature/Characters: AI, hologram
Locations: virtual world, matrix, terminal control, holographic platform, monitor
Details: it has no gender, but it can take human form to appear to us. Malevolent or benevolent, it will look cold. Digits run across it and it can access any system.
Do you think we can organize Team Battles? I think it could be a great thing to have several groups (not too many) working on one topic. For instance, it could be one-entry/one-participant or one-pic/one-team. Whatever the configuration is, all the members of the same team could help each other on their personal or common painting. This is basically a special form of Character of the Week activity on Concept Art, but I like the idea and it would be great to use it here.