I generally always use: Art, DigitalArt, ArtTag, OC, OriginalCharacter, as well as Sketch or Illustration I also have a personal OC tag (MicahsOCs) that adds to my own OC Feed + I recently did a second OC Feed (OCTalks) that is full of lore rambles. I'd assume there are more tags I don't know.

If you have art that fits into specific stuff (Dragons, Elves, TTRPG, furry, etc) always tag for that as well. Elves specifically have the ElfEnjoyers Feed for example. I am still looking around for OC tags that fit my stuff and often just do a lot of guess work.