How to Edit Icons

[Sam08]

Hello, I have a boatload of sprites I'd like to test in SP. I'm having some success translating them into the palette, but getting them in-game is a bit harder:

For example, I want to replace one of the T-72 icons. I found the hull and turret (image #'s 59 and 60 in Icon0004). Loading my bmp into SHPedit seems to work, but after converting my bmp to a shp, then I can't seem to replace the icon.

All I seem to create is a SHP with just one image (my new one). I can never seem to get to the button 6 where I replace the image in the collage.

I hope this is something simple.

Also, does anyone here use GIMP for this? GIMP is great for translating my images to the SP colors, but saving a bmp that SHPedit can use does not seem to work. Paint.net does, but I think the problem is more than just GIMP's desire to create 32 bit BMP's by default.