This is from Eric Homan - V.P. Developement at Frederator Studios from the Channel Frederator site: http://raw.channelfrederator.com This is what they want to see...
Know that a pitch bible and a writer's bible are two different beasts. The latter is a much broader document created after a show's picked up, the former is designed to give a brief but clear overview of what you want to do with your cartoon.
Everyone looks for something different in a pitch bible. I like to see a very brief overview, a few character descriptions, a bit about the world in which the characters live, and a handful of storylines. Make sure your storylines are brief but that they contain a beginning, middle, and end (i.e. no "Ben and Jerry get jobs at a car wash and hilarity ensues" or "Lucy has to cook dinner for Ricky's new boss - will she be able to pull it off?"). Three or four sentences should be enough.
Be as brief as possible overall. A total of twelve to fifteen pages should suffice. A paragraph or two, using the right language, should be more than enough to give an exec the information they need to decide if they want to see more of that character. Put yourself in the exec's position - what would you like to see? Remember, most development executives see an awful lot of bibles, many drastically similar. Be short, sweet, and distinctive.
Include a mix of artwork. Not everything should be finished or finalized, although I always like to see one piece of art showcasing how the creator envisions how the show will ultimately look. However, remember every project goes through a lot of development and will look different than what you initially present. One more note: I, personally, dislike character art in which your characters are more or less standing there, as in the standard model sheet pose. I see it all too often, when I'd rather see the characters doing something that reflects their personality.
Keep in mind the purpose of a pitch bible is to get a network interested in seeing more, kind of like a movie trailer. It's a first impression and should grab attention.
Good words of advice!