A program for creating maps of non-standard sizes.

I remember seeing a program somewhere that could cut out parts of maps (or the entire map) and allow you to insert them into other maps. I want to generate 144x144 maps and combine them.

Added 7 minutes later
Maybe someone here knows about it (although I doubt anyone would take on this task). I'm asking for a way to make the editor generate random maps, at least 1584x1584!