I replied to your pm this morning and included instructions for GIMP. I'm so sorry I was gone when you needed help. It seems Lewanda and I use completely different methods for aligning them, though. So I hope I haven't confused you. (I replied to all my pm's before I read the forums.)

I actually use a complete map, with guidelines in place where the map divisions are. I mod the "room" I'm working on in a separate (and much smaller) file that has only the room I want (the remainder is transparent and the image is cropped to just the room.) When it's done I "copy visible" to the combined map as a new layer (I never compress the layers as I've always got something else to fix. lol) Once the mods are on the combined map, I just let GIMP split it up into the map sections for the game, using the guidelines at 512x512 pixels.

I hope that makes sense... I agree with Lewanda - I wish I could just sit down beside you and show you!