Made by RogerN 

This is a utility for mappers to quickly add metal patches to their maps. It also creates a corresponding metal map. You must provide your map texture, height map, and one or more images containing tiles to be used as metal patches.

Adding metal patches is as simple as clicking on the map. The selected metal patch can also be randomized after every click, so that the same patch is never added twice in a row. All metal patches can be moved around by dragging, until you save the final texture.

This tool is written in C#, so you must have the .NET Framework 2.0 installed to use it. Also, please note that it will likely eat all your RAM.