Here's my first go at some basic empty tiles of a moss-covered stone floor. Nothing fancy, but I'd love any feedback. Especially as I'm selecting brushes to work with in GIMP, if anyone has suggestions for a "tree root" brush I'd be grateful.

Right now the closest I've found is a couple of other brushes combined with "Dirty Roots" (by Hypnotiza)...I'm looking at Brusheezy, Obsidian Dawn, and Deviant Art for suitable brushes.