This may help: http://www.mp3tag.de/en/

It allows you to add/modify any most tag info. You can download the album cover from anywhere resize it to a suitable pic size (300 pixel by 300 pixel is enough for the iphone/ipod 500 pixel for ipad ..etc), convert it to jpg, and modify the mp3 through mp3tag to have the picture inside the file.

Tariq

M80v2 - VP180 - S:QS8 - SB:QS8 - SWide:QS8
Denon 4311 + XPA-3
Sub: Dual SVS Ultra-13