1. Paint the wall with at least two coats of the desired base color. Allow the wall to dry thoroughly between coats and before proceeding to Step 2.
2. Create the textured look. Mix a darker paint (either latex or oil) with a glaze, following the directions on the can, or use a premixed glaze. Then apply the glaze mixture over the base coat with a crumpled rag or piece of paper, making sure the rag or paper has only a light coat of glaze on it. Allow the wall to dry.
3. Make cardboard outlines for the "stone blocks." Cut three or four pieces of cardboard to the desired size, making sure to keep the size of the blocks in proportion to the expanse of wall and the size of the room. Make big blocks for a large wall (too many small blocks will look dizzying) and smaller blocks for walls that are broken up by windows, doors, or cabinets.
4. Lightly trace the blocks on the wall with a charcoal pencil or chalk, creating a pattern that intersperses blocks of varied sizes. The more precise the lines, the more formal the end result will appear. Rough edges will impart a casual, timeworn look.
5. Paint the outlines of the blocks with an artist's brush, using dark brown, brown, black, or gray paint, depending on the colors of the stone.
6. Finish. Protect the wall with a coat of varnish, if desired. Leaving the wall unvarnished will keep it looking more natural and less like wallpaper.