There's always the option of a dig box. I've seen a tank set up with a 2x4 across it blocking off the end of the tank, filled with a digging material. I've also heard that rabbit feed pellets work great in dig boxes... no smell, little dust, etc. My tank's not quite big enough for this, so I use just a towel that Taz will dig around in and burry himself. Hope this helps on the digging side.
As for a non-particle substrate that's easy to clean... try shelf liner. The kind with out the stickey back. It's non-absorbant, and super easy to just wipe clean! And cheap to buy... that was the deciding factor for me. It's easier to keep clean then repti carpet, and the one I got works great in the set up, looking like sand. Taz's basking spot is the top of a cave I built from slate rock peices, so the hottest heat isn't directly on the liner, and I've never had problems with it melting or anything like that. If you go that route, just make sure it's non-adhesive. The stickey backing can melt and make fumes.
You can also try sealed tile... places like Lowes and Home Depot can cut them to fit your cage, and you can either grout them in and seal it, or line the bottom with news papaer under the tiles.
Repti-carpet is another option, but to me, it's hard to clean. You can't really spot clean it... you have to take the whole thing out, soak it, rinse it, rinse it again, hang it to dry, etc. And it may not come in a size big enough for the tank you're getting.
Other then that, the best idea I can think of is newspaper, and that's functional, but not pretty.
Hope this all helps, or at least gives you some ideas.
Kristen