Villagestreetwear.com sells a couple hair dye brands besides Manic Panic, and there are some pictures. Also check out the colored wigs there, they've got lots of bright colors.

This one too, if you click on the colors most have pictures of actual people with the haircolor, so there's some good inspirational style.

Also, for most things costume related, including hair dye... Costumes.org has tons of links to look through in categories. Have fun. :)

-Molly (well acquainted with the world of hair dye)