So, I extracted a screenshot, recolored it, saved it as a TGA file, and placed it in the map in UI/H5A2/Creatures/NecropolisSecondUpg/name.tga; and also in model/.../.../name.tga.
Then, I opened the map using WinRAR, found the file in model: something like DeathKnight_Coat.xdb. Inside, there are Scr_name and Dest_Name. In the first, I wrote a long path through UI, and in the second, I directly wrote name.tga, since it's in the same folder.
I opened the editor, checked, and everything matched, the links appeared. I decided to check how it looks, selected it, and the editor crashed. What did I do wrong?