Cover images for your movies:
If you want to have your iPad3 display cover images for your movies, you can use iTunes to add them.
First, download the image you want to use from a website like albumart.org or just use IMDB or Google.
A Civil Action (1998) - IMDb
then right-click on the image and select save picture as.
With the cover image downloaded, find your movie in your iTunes Library,
right-click on it and select "Get Info"
Go to the Artwork Tab, and tap on Add:
and select your downloaded cover image.
After that, "OK" out of this, and your cover image will be displayed for your movie instead of a thumbnail.
Artwork is not actually synced over, so if you want to see the artwork for your movie on your iPad3, you will have to delete the movie from it and then move it over again from your iTunes Library.
In the "Get Info" portion of Apple iTunes you can do a bit more. You can group TV episodes, change descriptions etc. If you like organizing your videos, it is a fun place to be.