Sorry, I disappeared for a while due to IRL problems. First, your tool is great and I am going to prefer it among everything we have so far.
If you don't mind, I will post some suggestions here, that could be some improvement to the product:
1/ floating point data for x y w h corrections of background instead of integer for precise adjustment
2/ option to display grid. Your meridian and equator lines are very useful for background adjustment, but grid would allow even more precise control
3/ indexes for textures in toolbox
4/ option to show indexes of texture on map directly for people who define colors poorly.
5/ option to define texture colors. Some textures are identical in color. For me personally, it is hard to recognize all that green colors and stop putting northern forests or swamps in jungles
6/ I have exception on using areas tool, probably something is bad with my data
https://github.com/723Studio/X-Com-From-the-Ashes/blob/master/Ruleset/geosphere.rul7/ Custom textures. For instance, I have 15 textures, but I can see only 14 in texture tool.
8/ Not sure, but it seems I can't see point-like missionZones
9/ Right click option does not work for rectangles
10/ Support of making rectangles?
Could be nice if we would share different maps that can be used as background here =) For mine you need to apply correction: X -180, Y -91, W 360, H 182