Browsing through so called "Hip Hop" albums, I can't help but notice the lack of cover art. All I see is a different rapper with a variation of the same clothes, car, jewlery, and girl in the back. We've seen this image play out over the last couple of decades and yet it seems to have become a permanent staple. (Needless to say this lack of art is also reflected in the music).
Metal and Punk albums seem to be more in-tune to the importance of visual art. Just go into any record shop and visit these sections. In a glance, the rap section could be summerized by bling, tatoos, and wife beaters. A look into the metal and punk sections may have themes, though equally disturbing, presented in some form of visual art.
Downloads have threatened the album cover. It's true that a thumbnail is offered with most digital releases. This gives recording artists an opportunity to let listener in on the album's concept. But how many fans actually take the listening experience that far? Probably those who still buy cd's and records. (Try putting a low resolution JPEG file on your wall!)
Indie labels that haven't taken advantage of the expression cover art provides don't get it. Without a major breathing down your neck the possibilities are endless. So save your personal images for Facebook and put your music before yourself by giving it an illustration.