In progress/behind the scenes photos are always things folks like to see, especially if they're somehow funny.
Example: When making our table banner for conventions we BROKE photoshop. It wouldn't let us save anything because the file was too big (go figure 2gigs is a lot).
This dumb, stupid picture is the most shared thing we ever posted because other artists understood the frustration and non-artists just balked at the idea of a 2gig 'picture' file.
Other stuff people enjoy is just seeing the artist/writer in action. Like this photo of artist Havana using chopsticks to eat fries so she won't get fry grease on the finished pencil cleans...
or this photo of the team at our convention table (I think this was heroes con?).
The more you share of your process and talk with others about how they do things the better!
Also: Get yo butt on twitter and follow #webcomicchat , #comicbookhour , #comics , and #ComicArtistsUnite Start makin friends on twitter~!