On my PC, I have random epic ones like InuYasha in a dress or something like that. On my Mac, I have over 100 photos that change every few seconds. Sometimes I'll spend hours staring at the screen changing. X3
Practically monthly wallpapers and screensavers should be related to the 4 seasons. However, that's not always the case. As I agree with what the poll says, anything will do as part of a monthly wallpaper.