There are lots of free eye textures in the freestuff section. Torann has fantasy eyes on the first page with a search for 'eyes' in freestuff. 'do whatever you want but not sell' is in the license. Therefore you cut a eye outa the main picture with a editing program (careful to have the eye exactly in the middle of whatever you cut) and map it in bryce using 'front' etc. Will take a few tries to get it right.