Franssen tells us,
I make my images from my own photos, and never use stock. Some parts are computer generated — if I cant find an object I will draw it. I build my own landscapes by taking photos of trees and grass etc. and then putting them together. I also create my own buildings from photos I take of houses and castles around my town. I often make a little sketch and then go searching for the right stuff to take photos of.
Image credits: Photographs by Mattijn Franssen and used with permission