From LuxRender Wiki
Texturing in Blender for SLG
Texturing is an important part of any rendering done with any render engine. SLG supports textures for a mesh's diffuse color, bump maps and normal maps. All textures must be UV mapped to the mesh.
What kinds of textures are supported in SLG?
Color (Diffuse), Bump and Normal maps. They can be in PNG (with or without Alpha) or JPG format. See each map's section for details.
What about Specular/Reflectivity/Shadow/Other maps?
No, only Diffuse Color, Bump and Normal maps are supported at this time. A lot can be accomplished with just these three, however.
How I do I UV map an image to a mesh in Blender?
There are numerous tutorials on the internet about how to do this already, so I will only go over the basics here. See below UV Mapping section.
Can I use Blender's internal mapping features instead of UV mapping?
Not directly, but you use Blender Internal to apply the texture just the way you like and then bake it to a UV map and use it in SLG quite effectively. See below section on baking textures in Blender.
What about Blender's internal procedural textures, such as Voronoi, Clouds, etc. Can I use those in SLG?
Not directly, but you can use Blender Internal to create a procedural texture and then bake it to a UV texture that can be used in SLG quite effectively. See below section on baking textures in Blender.
Diffuse/Color Texture Maps
Bump maps allow you to create the appearance of extra detail in your model without the need for the additional (and potentially complex) geometry to actually create it. It is just an illusion, however - looking at your model from extreme angles will reveal that the affected faces are still "flat". This is very handy for adding texture, scratches, engravings, etc. to a surface.
If more detail is needed, consider using a Normal Map instead (see Normal Map section below). One advantage that bump maps do have, though, is that they are easy to create or edit yourself, where normal maps generally need to be generated.
The bump map image itself is just a PNG or JPG image file, with each pixel representing an intensity. The brighter the pixel, the farther that point on the mesh will appear to be pushed out in the direction of the surface normal.
(Images utilizing bump maps needed)
All textures in SLG must be UV mapped. This involves using Blender to UV unwrap your mesh and choose how the texture gets applied/stretched across it.
(Procedure goes here)
Baking Textures to UV Maps in Blender
Baking textures is your friend. It allows you to use Blender's internal tools create and map textures for you, and then creates a UV mapped image that can applied in SLG. In other words, UV mapping your images just got a lot easier AND you can use Blender's internal procedural textures in SLG as well.
(Procedure goes here)