Wanted to add:
My suggestion would be to make the covers be pulled from the game directories i.e. we drop in a cover to the root folder of a game and rename it to COVER.PNG
This might help with manageability so people aren't bothered with the hassle of looking up title id's and all that jazz.
It would also help in situations where there are multiple versions of a game but share the same game id (even though the game id on the box might be different) so therefore the cover doesn't match. I own a few of these kinds of games. Happens a lot with special editions and game of the year editions.