I recently discovered how to do this. It is mostly a 2 step process:
1. Find the image you want for the show, via Amazon.com or IMDB.com and save it to a local directory on the core. So you will need to do this from the web browser in the computing link on you core.
2. From the same browser open a tab or just use the existing window, fire up mythweb http://dcerouter/mythweb
- click the top link for recording schedules
- click the desired TV show recording
- scroll to the bottom, and there you will see a box to add an image
- add the image you downloaded from the above step. I download mine into a directory under /home/public/data/pictures/show-icons
That's it, now the next time you go to record a show, you icon will be placed in the video menu .vs the Channel Icon.
Hope that helps,