If you do not wanna spend the money or have no time for tools like Texturemaker and similar go to this site. They offer you (nicely catalogued) some (more than 1000) textures with normal and bump derivates, exactly like the Irrlicht users needs them for his shaders. It's well organised with an ad-free layout like OPEN SOURCE pages. Of course they advertise for their own product.
http://www.filterforge.com/filters/