I've been experimenting with displacement maps, perhaps you could use them to create the spines, the image below was made with small white circles on a black background as the displacement, (value 0.5) I think I could have achieved finer definition of the spikes but was using a relatively small texture map (720 x 835px) as its an animated texture

http://www.renderosity.com/mod/gallery/index.php?image_id=1391617&member