Pretty much every industry-level artist uses photo textures. Otherwise they'd never get stuff done. If you look at how much of the painting is actually brush-strokes, it's all very minimalistic and simple. Most of the "art" is lighting effects, color theory, proper geometry and laid-on textures, all of which has more to do with draftsmanship and technical knowledge of the program being used than anything else. All you have to do is practice.