i'm in the process of building mine using pieces of Styrofoam from a coffee machine, one suggestion ill make- don't make the cut on the Styrofoam too rough, it will come out looking lumpy. to emulate stone i suggest a smoother texture- get a fine grain sandpaper and go on way (not back and forth- make the stroke, lift up, go back repeat) to get a smoother finish, if your patient you can sculpt with this method. and try your hardest to scavenge your Styrofoam, cheap as it is, you can come up with some great configurations using stuff from appliances, etc. plus they're free. also, you can build up areas with the great stuff as well, its not just good as a gap filler. ill post up pics of mine so far, i just finished sculpting. oh and during the sculpting process, get a light that you can move around directed at the piece, it lets you see how light behaves with your creases and carvings, essential to aesthetics.