Ever pay attention to some bland atheistic in some custom maps?
Stuff that doesn't look quite right?
A good example would be where walls meet floors.
In many maps, walls meet the floor at perfect right angles, no coping, slopes, etc.
However, if you look at the default maps, they often have variance between the walls and the floors. Even a change in color before the transition helps.
Other aesthetic items help too.
Many walls painted the same colors get bland.
Small variances can both differentiate between different areas and help to sooth the eyes.
Although I do not map myself, I would like it if my voice were heard.