A series of comics set in the Fallout universe would be pretty fantastic, especially if Chris Avellone was the main writer.
If it was going to be specific to New Vegas, I'd love a miniseries that delves deeper into back-stories of each of the companions or other character in the game. Maybe showing how Lily's life was like, living in her Vault as a grandmother, then her dipping and subsequent life as a Nightkin, or Boone's exploits as a NCR sniper, and even Raul's life living as a wasteland gunslinger before settling down as a mechanic.
Or, if not the companions stories, I'd love to know more about the people of Goodsprings, specifically Sunny Smiles, Doc Mitchell, and Victor. How they all got together, maybe a little bit of how their lives were before coming to Goodsprings, etc. etc.
(I know some stuff will be explained in-game, but I think comics to expand upon the characters would be wonderful

).