When it uses photographs, this method of sticking various images on one surface is called "photomontage"
Such framed, picture-like, wood-relief collages offer the artist an opportunity to 
explore... [DOC] [TLE] Collage in painting - Flare Code [PAR] In the 19th century, collage methods also were used among hobbyists for ... on 
painting when the patches "collided with the surface plane of the painting.