Here is most of the concept art at least: https://imgur.com/a/qlQPQ. Some of the concept art is taken from panels and some of them were uploaded to the Star Wars website at some point.
The episodes that are about 2h could probably be split into two parts, that way most of the episodes will be about an hour long.
Edit: There are also clips from the animatics (of the first arc) available. Check the video called “Unfinished Clone Wars Scenes and episodes” on youtube.