In current design the thumbs are generated from the beginning of the movie where the frames are not very dynamic and most of time are almost the same. And with current design when the thumbs are generated only with a few seconds apart, 99% of the time it is same studio logo.
The thumbs should be taken with more time difference apart from each other, beginning, middle, otherwise they are not informative at all. The easiest would be to give users a control of the time difference or % of the movie between the frames used for the thumb generation. This relates both to video and to recorded tv thumbs.

Additional information:
Forum thread: http://forum.team-mediaportal.com/threads/thumbnail-generation-design-problem-thumbnails-are-almost-same-and-not-very-informative.120146/