If you want to make something "stone-like", you might try the Hypertufa Forum. The recipes for hypertufa vary, but it is lighter weight than concrete or stone. Be sure to check out the FAQ section also.

http://forums2.gardenweb.com/forums/hypertufa/

this page might help also :

http://forums2.gardenweb.com/forums/load/hypertufa/msg031758554173.html
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anotherchris

also check out the Garden Junk Forum. There are tons of ideas there. http://ths.gardenweb.com/forums/

You could probably paint on signs, planted chairs, etc. Here is a plate idea someone posted there a while back.

Here is a link that might be useful: plates

You could use canvas and paint large or small flags. There are cute metal holders for both.

Wooden benches are good surfaces to paint on also.

Be sure to check the posts and pics at the Tole and Decorative painting forum too.

Here is a link that might be useful: Painting forum

I probably should have mentioned that I already have memory stones there. Here's a link to one of the things i want to print. I kinda like the wooden bench idea.....

Here is a link that might be useful: The House Dog's grave

Too many pets, that is a beautiful tribute, but would be allot of words to paint on something. Why not print it out on pretty paper and seal it in plexiglass? Then you could mount it on a stake or hang it on a wall. Good luck with your project. Luvs

I'm trying to come up with something now for something sort of similar. My MIL wants a poem written on something to sit at her son's grave. We were thinking a piece of slate but we're not sure. Maybe a ceramic tile or possibly the fake stone used to cover houses (my Pap has a few cases left over from his house). Whatever you choose, be sure to seal it really well. That's the only way it will last and if you can help it, take it in out of the harsher weather during the winter months if you get freezing spells and snow where you live. It will save you in the long run!

Good luck!