  Procedural content generation (PCG) can be applied to a wide variety of tasks
in games, from narratives, levels and sounds, to trees and weapons. A large
amount of game content is comprised of graphical assets, such as clouds,
buildings or vegetation, that do not require gameplay function considerations.
There is also a breadth of literature examining the procedural generation of
such elements for purposes outside of games. The body of research, focused on
specific methods for generating specific assets, provides a narrow view of the
available possibilities. Hence, it is difficult to have a clear picture of all
approaches and possibilities, with no guide for interested parties to discover
possible methods and approaches for their needs, and no facility to guide them
through each technique or approach to map out the process of using them.
Therefore, a systematic literature review has been conducted, yielding 200
accepted papers. This paper explores state-of-the-art approaches to graphical
asset generation, examining research from a wide range of applications, inside
and outside of games. Informed by the literature, a conceptual framework has
been derived to address the aforementioned gaps.
