This example of photomontage works well because it is visually interesting and has a lot of contrast. The photo of the woman is in black and white while the photo of the plant is shown in color this contrast makes the image stand out more.
Self portrait ideas Mapping 2013 on Behance Use a process like this for "identity/self-concept" activity about skin color/shade/tone/palette. Put vertical photo strip of every child together on a couple images to make a collective face.
Edit // sew two portraits together to create a mixed media piece // Manny Robertson- Embroidered Metropolis. ((Each original print is composed of two portraits, one color and one black and white, that have been cut and sewn together by hand.