If you're saying that when you're trying to load the height image into the map, the game crashes, then I believe it's not a big problem. If you're using gimp all you have to do is this:
-open the heightmap image into gimp.
-Then at the top of gimp it says Files - Edit -Select - ECT - ECT...
-Click on the one that says 'Image'
-Near the bottom it then says 'flatten image'. Click it.
-Export it as 'HeightmapNameHere.png' , make sure it's .png
Same thing goes for the color image.
I'm sorry this doesn't completely related to what you were asking for, but I hope this fixes your problem with the crash. ;u;