Several players are quite displeased with BluePwnsU who revealed the secrets of obtaining wanted posters on Reddit. The sale of Wanted Posters have been very lucrative.
You can get bounty posters from pick pocketing guards.
I have personally picked 5 different wanted posters: Khajiit male, Orc female, Imperial male, Colovian male, Breton male.
If you are wanting to decorate your house with some wanted posters or make a bit of coin, brave the guards and pick their pockets.