Channel icons
From MythTV Official Wiki
As of 0.21, MythTV includes a channel icon downloader in mythtv-setup which will automatically download the icons for channels it knows about, or guide you to find icons for channels it doesn't.
One of the best sources of channel icons is http://www.lyngsat-logo.com/ . There, you can browse the available icons and choose those appropriate for your system. However, doing so can be a lot of work (requiring many page hits and a lot of time).