I put together a few terrariums recently. It all started with the finding of some great glass bowls at a thrift store for 50 cent.
One I filled with about four different types of moss I collect from sidewalks, parking lots, and swamps. I made a put down a layer of soil, then the mosses, and to top it off I added a bird skull, a feather, and a petrified rib bone. For the holidays I wanted to get festive so I added the red berries, and I loved the way the contrasted so I just left them.