Robert McQueen:
I was able to trick iOS 7 into showing album art instead of the artist photo. I noticed the wrong artist photo was pushed for the 60's band Cream. No idea who is in the photo they're using, but it was clearly not Cream. I found that by changing the artist name by adding a space immediately after the artist's name in the "Artist" field in iTunes it would show album art instead. When I made that change in iTunes on the computer the incorrect artist photo was replaced by album art.
I am using Match, so the change was pushed, but I imagine it will work the same if you add music manually or sync the music library with iTunes.
For those that want the artist profile photo, if they're not showing this ought to work:
If you don't have it set this way already, toggle "Group By Album Artist" in Settings->Music. For some reason that makes a difference for some artists in your library that appear when album artist is set to "Various Artists" or something other than the track's artist. Logout of your Apple ID. Log in with any other Apple ID. Open the Music app and watch all the artist images load in the Artisits tab. Once it is done, logout of the other Apple ID and login with your regular Apple ID. Finally, all the artist images will remain. Those artists that do not have a profile photo with iTunes will still show album art, which is by design. Hopefully Apple will keep updating that database.