After having recently watched walking with beasts I am thoroughly loving the idea of creating some new fantastic creatures myself XD
Bet you can't make anything more fantastic than Opabinia :D
Hmm, I should watch WWB some time. I've seen WWDinosaurs and Monsters, it's really a shame I never took the time to watch the third *eyerolls*
Opabinia is made of ultimate WIN !!!
Hallucigenia is, too.
Actually, you could also play around with plants a lot... This summer I went to a plant science summer school, and the ice-breaker group exercise we had was to design plants for various man-made environments. You can't imagine how much fun we had XD Aphrodisiac-producing flowers that rely on people sticking their noses inside them for reproduction... and that was one of the less wild ideas.