2012 MBA Screensaver not working

Hello .... I am having a small problem with my MBA screensaver .... I am trying to set the screensaver to display my iTunes artwork in System Preferences, however, when I click on the iTunes Artwork button, I get a message that says "Your iTunes library does not contain any any songs with artwork". This is clearly not the case since I have over 1,600 songs, all of whick contain the appropriate artwork. Anyone have any ideas on how to fix this? I realize it's only a minor issue, but annoying nonetheless. Thanks for your help !!