Well done, they look great. (Although... did we have green lobsters?)
Just as something I would say to anyone making such graphics, though, looking
distinct is often more important than being beautiful by itself. The crazy poses of the kings and queens and jacks on playing cards or Egyptian hieroglyphs , for example, do not show a very attractive image, but they show very easily recognizable images - you can tell the king is holding a sword or an axe right away because it is being held away from the body so that you can clearly see the silhouette of the item.
Most of these are both distinct and attractive, but that second one (baby sunfish?) looks like a spiky ball, the baby horseshoe crab is too small to really make out.
It's a minor gripe, as well, but the smaller lobsters are also a little hard to make out - if they were viewed so that you saw them from straight overhead, so that it's a body with a few legs and claws coming out, the image would be somewhat simpler, and easier to identify. The color contrast on the body makes it a little hard to make the overall form hard to make out, and I didn't recognize it as a lobster until I read the text beneath.
EDIT: Oh, and it's just a little odd to see a "skeleton" creature whose form is defined by its exoskeleton...