To start with, I will explain a little about matte painting. Matte painting is where you use a texture to paint an image to make it look realistic. This is an example:
I took two royalty-free textures from textures.com and incorporated them into the drawing. I still have to shade, highlight, and create the perspective to get it to work in the image. The textures are on the ground— the rocky ground. The other is on the wall. It gives the image a realistic feel even though not everything is texturized.
Another recent example: