Here you will find some examples of the different levels of detail in a mural.  A low detail mural may have only 1 or 2 colors and line work instead of shading.  A high detail mural will have a large variety of colors, tones, and more components in general.  Some things are simply more difficult to paint and will bump the artwork up a level, for example; portraits, photo replications, and certain textures.

Low Detail Murals

Medium Detail Murals

High Detail Murals