Christopher_Alexander? used this format for his architectural Patterns:

  1. A picture, showing an example of the pattern. (Pictures are easier for buildings; for games, some games that use the pattern might be more useful.)
  2. Connections to larger patterns that this pattern completes.
  3. A statement of the problem in one or two sentences.
  4. Background, justification, options for use, and other details: the largest section.
  5. A short statement of the solution: the pattern itself. Stated in the form of an instruction.
  6. A diagram of the pattern. It remains to be seen whether this is practical for games. We also have to sort out the images in the Wiki issue.
  7. Connections to smaller patterns, which complete this pattern.

Source: A_Pattern_Language?.