There has been a pretty significant decline in activity during the three-and-a-half years that the site belonged to Gamefly, until the end of 2013. I guess the catching-up is still going on, but new submissions don't tend to remain pending for long anymore.
Also, if I'm not mistaken, approvers can handle items in any order, so it's possible that some older but more difficult to verify entries keep getting pushed down the queue.
Yeah, backlog on new games/screenshots is down to a matter of days. But there are a couple of queues - particularly escalated things and weird 'exception'-y things like companies - where we are still digging out from a number of years ago.
Something from 2008 was approved in the last two weeks for example! (I don't think that person turned up on the forums yet :P)