I pulled down eracoon's landscape tile set from Blendswap. These are nice looking tile assets that can connect together to form various landscapes. The first thing that came to my mind was that these should be hooked up to some kind of procedural generator to make random tile based layouts.
I am working an AddOn that adds a TOP/BOTTOM/LEFT/RIGHT property to each of the tiles. The AddOn also has a Generate button to randomly create a grid based layout from the assets. I have extended the data type to include a few flags as well such as Enabled, Is 2x Asset, Filler and Buildable. Any tile can be removed from appearing in the scene by turning off it's Enabled flag. All tiles are enabled by default. A 2x asset is a tile that takes up 2 spaces on the grid instead of 1 like all other tiles. When filler is turned on that tile can be used to patch holed in the grid. If buildable is turned on that tile can be used as a spot to build a 2x asset.
Here is a short overview of the new layers in Tile Proc-3.
Here is a short video tutorial on how to use the new Layer features of Tile Proc 2.
I put together a short video tutorial on how to use the Tile Proc 1 AddOn.
The AddOn uses the texture_space dotted outline of an object to highlight which tile in the scene you are currently editing.
Here is a 1st draft example of a purely random generation.