Player housing has been on the World of Warcraft wish-list for just about forever. Periodically ingenious players create and share concepts for how player housing could look, might work, and would be awesome. Check out this extremely detailed concept from the appropriately named WoW_housing_idea. The amount of work and thought that went into this is absolutely staggering.
Concept for Player Housing
(Note: minor edits for readability)
Why add player housing?