JEplayer can show artwork to go along with each track or album. Make your artwork up to 160x96 pixels and be sure to save it in uncompressed ".bmp" (Windows Bitmap) format.
Put the image alongside the mp3 files in a folder. To apply it to all tracks, call it "cover.bmp". To apply it to a single track give it the same name as the mp3 file. For instance, if your track is named "03 Neat Please.mp3" make sure the image is in that folder and called "03 Neat Please.bmp".
If you downloaded Bartlebeats, here's the album artwork converted for you: