You need to define rules that can be met by the selected items, and a custom image file to be used as the logo. In the example above I think he used a rule to say if vid resolution is above x display this jpg, if no of audio channels > 5 display the 5.1 logo and based on the network display a <network>.jpg.
Please read my post in the tv-series forum for a step by step guide.
Inker beat me to the explanation.
Although Inker imo the HD and the Souround Logos should be hardcoded values because
1) A video file is not considered HD if it has any resolution lower than 1280x720
2) A video file with less than 5.1 is not consider do have souround sound.
hardcoding and including default icons for those 2 will make it easier for most people to configure it as they will have nothing to configure
just my opinion tho.
Cyprus