Jim would have to answer this one himself to be sure, but most of those require the 3d background to be truely realistic.
Mandarin Goby; It is a beautiful fish that inhabits the lower regions of the tank, often burrowing into the substrate.
Seahorse; have you ever watched one? they actually swim very very little, they spend most of their time with their tails wrapped around something holding on. Currently the coral you are looking at is in a flat plane, there isn't anything to wrap around.
Shark; doable to a certain extent, depending on the species and how much they swim and/or rest on the bottom of the tank.
Eel; I had one for years, a Zebra Moray. Actually the photo on the wishlist page is the one I had. ( Jim said he would/might make me one for my efforts, if he got the chance. I haven't forgotten Jim
) Moray's DO NOT like the light. They generally live in holes or caves and come out mostly at night to feed. It was one of the options that Jim liked and wanted to work into his aquarium. You would be more likely to see the eel when your lights are dim. But, he has to have a 3D cave/coral to be in alot of the rest of the time.
Sea Turtle; might be doable, not sure about this one.
Cuttle fish; I would imagine that getting the movement of this one right would be a bear. I am sure that Jim would get it right from looking at his past work, but I would imagine it will be time consuming.
Another Starfish; might be the easiest one depending on if Jim chooses to use the same model or create a totally different one.
Realize that these are only my thoughts and I may be way off base on some of these, I am only thinking out loud.