This canvas is covered in paint chips to make up Marilyn Monroe's famous visage.
This Abe Lincoln piece is a canvas with painted squares of varying colors of grey.
"The Lincoln portrait was done by pixelating a photo and boiling it down to 9 shades of gray (both done in Photoshop). I built the canvas, gridded it off in 2 inch squares, and mixed the different shades of paint. At that point it basically became a paint by number" - from AT.