Snackbar Games is engaged in a neat project to create box art for the entire Game Boy Advance library. These art files can be printed out and slipped into the nice Nintendo DS cases that keep better than the cardboard GBA boxes. The high resolution file (much larger than the one you get from clicking below) might need some processing before you can print it. I had to make sure it was set to print 300 dpi and at 10.9 inches width. To ensure nothing got cut off at the margins, I printed the art as two separate 5.5 inch sections, but that's not necessary if you can set 0.25 inch borders on your printer. You can find over 450 other pieces of cover art here.
And here's a few shots of the finished product! You can order empty DS cases from Nintendo here.