Display if Cover Art is Present
I used the following expression to really streamline my [Image File] column for view schemes, and it stops it from doing wild and crazy things when the columns are resized after tagging - and it's great!! All I get is a yes or no, instead of a big long file path. 
FormatBoolean(IsEmpty([Image File]), No, Yes)
I used the example from EpF, but for the covers I don't have, instead of leaving them blank I have a generic image called nocover.jpg so that something is displayed in Playing Now. My cover art is stored in the coverart folder. This still displays a yes or no.
If(If(IsEqual(mid([Image File], 1, -1), :\mp3\coverart\nocover.jpg, 1), 1, If(IsEmpty([Image File]), 1, ) ), No, Yes)