Hiya frlejo! =)
You didn't say what you had in the tank now, so you may already know this but...
It might be fun to get a few pieces of good quality live rock and just see what comes of it. I ordered rock for the 90gallon I'm running now and had some left over peices after I was finished with my rock scaping. I just placed these extra pieces of live rock into the sump to help with filtration, not thinking that they would have any life on them that would grow in thier no-light environment. You can imagine how suprised I was when after several months I went to move them from the sump into a newly added refugium only to find them covered with spongy growth, tiny
tube worms, a tan colored corraline-type growth and some mysis shrimp! =D
And like Work said, you do have a *huge* array of mushroom colors to choose from! Also a
christmas tree coral should do well for ya.
A weekly water change using a quality salt mix should replace needed trace elements. And then a suplement like the Sea Chem Reef Plus that Work was talking about can be used sparingly to encourage growth and color. =)