Here is an image of Eric Carle's book. I think it's beautifully illustrated, and tells unique facts about seahorses in the text.
And, yes, I did get this idea on Pinterest! The pin that inspired my lesson has the seahorse decorated with beads and buttons, which I thought added some nice visual interest, so I let my students put sparkles on their seahorses. I know that sequins are craft supplies, and don't generally have a place in the fine arts world, but the kids enjoyed it, and it provided one last assessment of their learning of the warm/cool color concept, because they had to pick out the warm color sequins from a large tub of various colors.