Okay, click devices on the left hand side of your iTunes.
Then click you iPod, whatever it's named.
Second, up at the top of the iTunes window, underneath what shows what's currently playing, there is a tab labeled "Music". (On my iPod Nano, it's between Summary and Podcast. I think it's different if you video can play videos.)
Finally, there is a check box in the "Music" tab that says "Display album artwork on your iPod". Make sure that isn't checked and you're good.