Gaming for (Painted) Dragons -
Home of Stellagama Publishing
Those bases have come up very nicely. If you're able to, try and get some model railway flock (sometimes called static grass). Games Workshop has a range but the model railway stuff is about half the price. I use both static grass and thicker, chunkier stuff for little bushes to help bring the bases up. I also use fine and coarse sand on my bases, depending on the effect I want to get - fine sand painted a flat grey looks quite good for asphalt surfaces or even interior floor sections.
Once I'll have more available funds, I'll definitely buy some flock or moss... :)