I'd like to echo Larry's sentiments; a glimpse into the selection process would be nice, or something. I've uploaded a number of covers that I thought were really good but still haven't appeared on the site, and then sometimes I'll see something get uploaded to the forums and then basically immediately uploaded to the site proper the next day, if not within hours. It's really disheartening to see (even though I know it's not personal), especially when I have no idea why my covers never get posted because I'm never told what's wrong with them or how I can improve them, or even if there's nothing wrong with them but they're at the end of a long queue.
Perhaps some kind of feedback system could be implemented where the person who submits the cover gets an "anonymous" response from the Admin team (ie: sender unknown on the user's end, but logs kept on the Admin's end) letting them know the status of their submission. If it's been rejected, the person should know why so they can try to fix the problem. If it's been accepted, a simple heads-up would suffice.
Just my thoughts.