It's a real bumpmapping shader so you need a normal map to make it work - the one I used is here
. Normal maps are a way of storing 3D data on a texture, which the shader then uses to calculate 3D lighting. Bumpmapping is well documented in 3D so I looked at the shader and pretty much just got rid of the Z axis, and tweaked it till it looked good.
There are plugins for Photoshop and Gimp that can turn a greyscale heightmap in to a normal map so it's still easy enough to generate the textures you need for bumpmapping - but it does make it a bit trickier if you want to do a fullscreen bumpmap on all the objects moving round. I'm not sure if thats possible.