Sorry for the late response - wasn't around for a while.
Yeah, what Sark said.
For the colour variety on the leaves, open the brush palette, choose "Colour dynamics" and set the "Background/Foreground Jitter" to a fair percentage. I used a darkish green as background and a dark red for foreground - the colours came out a bit dull, so I changed the curves for it a bit (Image --> Adjustements --> Curves). Add two points - one low, one high and adjust (to a sort of rollercoaster peak) - you'll see greater colour vibrance almost immediately with preview active.
You can also use the size dynamics to get size jitter to taste.
For the texture settings for the brick wall, my Relief was set to about 3 or 5, with scaling of 167%.
Re: Using textures 
Linear Mode
