I'm in the same situation
My DM allowed me to use Epic Shifter (http://www.wizards.com/default.asp?x=dnd/ei/20031010a
), so Supernatural Abilities withhout the need of many feat slots, see with yours if its possible
For forms, i haven't though a lot about them, mainly Redcaps from MM III, they keep advancing in power with you, so it's a good form overall, in any occasion, Gloom from ELH seems extremely userful and also Ha Naga from the same book.
But who knows, maybe someone can help you (and consequently me) more, i'm still developing mine