This is really cool and creative. I might do something like this. You could create two templates, one with the portrait and one without and paint the cardboard 2 colours for a great kind of Scarface effect
French painter and collage artist Anastassia Elias creates tiny scenes with paper inside cardboard toilet paper tubes. Anastassia uses paper the same color as the cardboard tubes to build up the intricate pictures of people, which gives the illusion that the scene taking place inside the walls are actually part of the roll itself. The models, which sell for £90 each, come alive when light is shined through the roll from one end. The details and depth of each piece is impressive.
Rather than simply throwing away a cardboard box, artist Giles Oldershaw redesigns the discarded packaging he comes across as creative, layered portraits. By carving and tearing away at the material, Oldershaw exposes the ribbed texture sealed within. His meticulous precision and artistic ingenuity results in a spectacular set of Cardboard Relief Portraits. Mr. Peter O'Toole