Procedurally generated wallpapers.
Ranked in these QuestionsQuestion Ranking
Yup, because they're randomly generated, you can use this offline, in the middle of absolute nowhere.
Pro Rotating wallpapers
It does what it says on the tin.
Pro Infinite wallpapers
Not technically, but at least infinite enough that you will never see the same one twice.
Con Only a few types of patterns
They all look amazing, but just something to note.