get some foam, then glue chunks of polysterine onto it, smoothing it out how you want, sand, sand, a few different coloured oxide, cement mix.... very easy if your creative.
Sam, If you have the time to make your own, then do so. If you are not in a hurry, it will be much cheaper for you (and also a good experience) for you to make your own.
If you want an awesome background and have a few bucks. I got the 6x2ft 'Olgas' fake rock backing made by universal rocks. (full laytex material) Got it through 'Canberra exotics' for a really good price and postage from ACT to NT was only $20 buck. (It was cheaper from ACT then locally) Can't fault them and saves time sanding, glueing and rendering, done both and and the universal rock is sweet looking. Once the cage is fully completed i'll post pics.
Both options work well, it just up to you which way you want to go.
I agree with you yommy, Canberra Exotics has the cheapest range & can mail order. WHen I was at the VHS expo the rep from Universal Rocks told me that Peter at Canberra Exotics is their biggest customer in Australia (for reptiles). If you want further info go to www.canberraexotics.com.au
yeah pete does have heaps of unverisal rocks products available, and he uses them in most of his displays and they look awesome, also a friendly guy to deal with