Portrait, Mid-body, or Full body?: Full-body.
Character species: Sableye. The Pokemon. ;o
Character deion: Basically, she's a very, very shifty, flowing sort of thing. Both because she's a Sableye and because she's made of mercury. Not really one of those characters where you can actually see it, since she does have skin, but she still has a little bit of a shiny appearance. Like a glowing shadow.
The biggest part where you can see the whole mercury thing is in her gems - instead of being actual stones, they're like solid drops of it. Especially her eyes.
A hint of female curvature could be thrown in too. ;o Heck, you could even just make her generally more humanoid than a normal Sableye if you want.
Reference?: No reference. This'll actually be the first drawing of her.
Mood/pose: Something like a predator who knows she's caught her prey unawares mixed with mischief.
Background color: Either dark like a cave or just no background. *shrug*
Flat color?: Yes.