Go for it, Cinta! You'll be amazed at how great this works. I've got two (I think) that are two years old, another one is older and those are all finally filling in nicely, and built two more this summer which are looking good. By next year, they'll be spectacular. You need a lot of plants; the best ones for me seem to be some of the little Sempervivum arachnoideum, those like Hookeri, especially. Then they pretty much cover the whole surface, and make almost a groundcover. The Sedum and larger types of Semps stand up over them. It's a great effect.
