I'd be warry of rocks from the "Craft Store". If anything, go to a river and find rocks yourself. (Then test with vinegar, soak in water for a while to make sure it doesn't change the pH etc.) People do use what's actually called "Pea Gravel" in aquariums. It comes in many sizes from smaller than a Pea, to almost normal gravel size. I read that in an aquarium aquascaping book so I trust it. Keep in mind that if you use bigger than normal substrate it's gunna make it hard to vacuum the crap (literally) out of it.
Also, just buy some driftwood. I actually bought mine from this website, and I got a few extra pieces for free.
Bob's Tropical Plants
<-- Also, I believe that's MGamer's site...
When I bought it the price INCLUDED shipping, so that's why it initially looked high. Best thing I ever did. I bought a small piece pack, and got probably 7 or 8 pieces. All nice ones too. Very good variety. Hmm, looks like he doesn't sell "Packs" anymore. Too bad, still a good site.