Let's see...
Well, a Dryad. Yes, feminine-looking, maybe branches for hands and feet, and it's footsteps could perhaps spring little flowers and stuff. ^_^ It's evil form, it's hands and body could be twisted and leafless.
![Good [Good]](/Emoticons/good.gif)
, it could have flowers growing amongst the branches, and birds could flock around her and nest within her.
A goat. The evil form could look much like Baphomet, minus his infamous scythe.
![Good [Good]](/Emoticons/good.gif)
form, well, that's kinda easy...
Maybe a pixie?
![Good [Good]](/Emoticons/good.gif)
form could be an angel.
![Evil [Evil]](/Emoticons/evil.gif)
could look like an imp or demon.
Yeah, simplistic, but sometimes the easy ideas are the forgotton ones. ;p