It can be fun to put the picture of a person or pet into an unrealistic, brightly-patterned world. If you want to do it, carefully cut the subject out of the picture.
For the new background, choose a colorfully patterned sheet of gift-wrap paper, wallpaper, or paper from a craft store. Or draw it yourself with markers, crayons, or paints. Paste the picture onto its new home. Now use a black marker to draw an outline all around it.