•Vendor

I visioned that the developer made the player either make their character like a vendor, or just center a game around it. A tycoon, perhaps?

•Inn

A theme like early 2000's MMO's where you can gather up quests, maybe even give one!

•Background Interacting w/ The Game

I don't think many games which has a blurred background has an interactive background system. But I believe that this theme could work in a number of ways: puzzle games, games where you know when the enemies are coming via the background, or just that you'd have to pick up objects from the background, who knows?