Bump Mapping, Fog, Alpha-Bending (transparency), Mip Mapping (polygon-texture auto switch), Tri-Linear Filtering, Anti-Aliasing, Environment Mapping, and Specular Effect.
Fog, Alpha-blending, Mip Mapping and Tri-Linear filtering is standard in KOS. I think you can easily enable Anti-Aliasing aswell, Although I didn't really see any effect in using it (it's only 2x1 AA).
Environment Mapping, well, AFAIK there is no way to send normals down the pipeline, but if you want something simple it's so easy to calculate the texture coordinates yourself. Just set u = 0.5 + 0.5 * normal.x and v = 0,5 + 0,5 * normal.y.
Specular highlight, use the oargb to set it, but you need to enable some bit in the pvr-header first. I'm not sure if this was ever implemented in KOS or if there was just some demos floating around showing it.
Bump-mapping, yes, I was the first one to figure it out and show how to use it. A (very) simple demo using bump-mapping:
http://www.boob.co.uk/files/bump.tar.gz
A tool for creating bumpmaps suitable for the DC from standard heightmaps:
http://www.boob.co.uk/files/dcbumpgen.tar.gz