Customs aren't bad. Remember, this site started out from the idea of making custom GBA covers for DS cases.
Likewise, as I said before, I could totally see importing a game (for example, a GameCube game) that comes in a totally different style case and wanting a cover that fits the style of the rest of your collection. Heck, my single imported GameCube title actually shares a two-disc case with the NA release of the game.
*and* if we're going to throw out all customs, the entire peripheral thread is done for. And I really like the idea of cases/covers for memory cards and such. And there's things like, say, Chibi Robo for the DS, where I requested a cover without the ugly "Only at Walmart" logo. Plus games like the original Guitar Hero DS, Wii Sports, Metroid Prime Hunters demo, etc., etc... These are some of our most popular downloads. (anyone have an actual list of our top 10 downloads?).