Here's a close-up of the final coat in the Study Bathroom. It's an antique leather treatment.
The base coat is the lighter color (same as the color in the study). The top coat is a darker brown mixed with 3 parts glaze. The glaze mixture is rolled on the wall and then covered with a thin plastic sheet. The plastic sheet has been pre-crumpled and then laid out mostly flat on the wall. When the plastic is removed, some of the glaze mixture is removed with it. The creases and folds in the plastic cause different amounts of glaze to be removed, giving this effect.