This was way too long on the 2.5 todo-list, but effecting particle properties with textures is now once again possible! It's perhaps not the "effect anything with anything" solution I was thinking about at some point, but then again I'd rather not over complicate the current particle system with a complex system that can be far better handled with nodes in the future.
This was just committed so get a fresh test build after r34798 and your're all set!
