I love the whole Xindi concept.
Count me as an Arboreal/Sloth fan! Actually, I'm a fan of all of 'em. They are grand fun to put into fan fic (warning: I will now tell you about fan fic. Hide if you must
I wrote a little girl Arboreal and pictured her as resembling the Tenniel drawings from Alice in Wonderland
I've also got a human-Klingon-Sloth hybrid who's a doctor. Powerful and paranoid, a nasty combo. I see Henry Rollins there.
I also wrote a teenaged Reptilian girl (very Valley girl-like, picture her with a phone glued to her ear and constantly doing her nails - I mean, claws. Plus a Reptilian-human hybrid who is bullied and fights back with disastrous results.
Insectoids are kind of challenging to make sympathetic; I do have a scene where my heroine (she's Chef's assistant) whacks one in the face with a cast-iron skillet.
Haven't written Aquatics much yet, as they are tough to get into a scene with anyone else.