Up on the official Might and Magic portal is a short interview with famous comic book artist Olivier Ledroit. He talks about his work on Heroes V:

"For me the most interesting things in videogames is the fact that they allow us to animate the universes that are created. It is very impressive to be able to walk in a man-made universe, just like if you were part of it. I already worked with videogame industry in the past, but it was more difficult to see a direct link between what I had created and what was displayed on the screen... For Might&Magic, I took care to create characters where you could remove some details without breaking the general silhouette."

Read it all here (look for the second news article). The article includes several sketches of heroes from several factions.