I am using *.png, but what I meant was, what are the naming requirements, for the files, so that the skin selects the correct logo for the current channel tuned?
Filenames should match the longname (if present), or the shortname. For example:
BBC HD, BBCHD:...... it would be "bbc hd.png". BBCHD:...... it would be "bbchd.png".