IMG File Format
From Quest For Glory Mods
The IMG file format from Quest for Glory 5 contains indexed 8-bit pixel data from the game's panorama backgrounds. These files can be found in the 'CDN.spk' archive.
The correlating palette data for these files can be found in NOD files, also contained in the 'CDN.spk' archive.
There is a command-line program available for extracting and importing the backgrounds qfg5pano. The source code is available with the download, which further clarifies the structure of the files.