I once saw a series of halloween costumes based around Alice in Wonderland, which were pretty good too - a bloodstained, psychotic Alice, and I think there may have been a horror version of the Mad Hatter too.
Yeah a cat sounds brilliant.. you can paint on the mask if u cant get hold of one and do whiskers, a little nose and ears aswell which always looks cute. i went as an angel a few years back because it meant i could look glam and gorgeous yet still be dressed up!!! plus, angel wings are just sooo cute!! and you can easily make you own.. 4 old coat hangers, some white/pink tights or material (cheap down the market!!!) and some glitter, stickers, sequins, anything!!