I was peeking around at the Dark Sun website and found a list of Dark Sun Monsters (in .pdf format) (http://www.athas.org/releases/ds3/monsters.20030331.pdf). It has pictures of some various ones that are in Arm, such as mekillots, tembo, kank, braxat, and a few others. It's pretty interesting to see and a good way to get an idea of what things look like, although I think one or two things aren't 100% like Arm creatures.