Thanks guys!
It's been so cool to watch the tank develop. I believe the carpet is an S. Gigantea, but the LFS didn't have it labeled, just as a blue carpet. It is over a foot and a half across when opened, and I got it for 30$!! The urchin isn't carrying eggs, those are its tentacles when not extended. It actually moves by these tetacles, extending them out past it's spines, and as you can see, also uses them to attach camo.