There are two types of textures, image and procedural. Image textures can be made in photoshop. Procedurals are made by using equations in the DTE to set up waveforms.

Go to the top header in this forum and click Bryce Backroom. Click on Bryce Links. Scroll down to Bryce Websites and read everything there. That will answer 99% of your questions. Paticulary usefull to you will be DTE tutorial part 1 by Susan Kitchens.

We did a DTE challenge in 2003 the challenge mats are available here. DTE Challenge Mats

Excellent set of wood and metal textures at Tony Lynch Designs.