Commonly called ‘manips” these are produced by manipulating screencaps or photos. While strictly speaking, much fan art uses digital manipulation of some sort, the term is used specifically in fandom for art which uses, for example a characters face, on a body taken from a different person.
The subject matter is diverse, two major areas for this work is either Crack or often sexual in nature, featuring nude images or the production of Wincest or Slash images which may range from portraying the brothers kissing to having sex. Manips featuring characters with wings are also popular.
While there are many excellent artists in this area, many bad images abound, commonly described as the “head is pastede on ya” variety where it is obvious where the images have been (poorly) cut and past.