A few more suggestions:
I really like how all the corals were clearly priced. The little specimens tanks desperately need some pricing though.
Something that would be really cool would be information cards about the corals and fish: A laminated page with a picture, common name and scientific name along with a short discription about care (water flow, lighting, diet for fish, difficulty). That way someone browsing can read a little about what they want and see if it is right for them. I personally don't like to ask questions and that would be great for people like me.
You need a nice display tank. While the frag tanks work very well, I love the look of a full display tank; that's part of the reason I love going to stores to get ideas with what I can do with my tank. That and seeing something so spetacular is what got me into the hoby to begin with, a good way to get new people who just stop by to browse. And you can still sell the stuff out of it too.
If someone stopped by and said they wanted to set up a complete tank, could you sell them everything they need on the spot? That's what my dad's friend just did.