Did you ever think of charging people to use your website? Like a subscription, maybe even a one time subscription. Offer them three covers for free and then after that require them to subscribe. To be honest ads don't always make as much money as sales.
Could you please post a link to your site, so we can have a look at it. It's hard to tell you how to optimize your earnings without seeing your site. Also, have you shoped around with hosting is $150 the best deal?
The site is c o v e r g a l a x y .com
My old webhost wouldn't host me anymore so I got a dedicated server so I could control everything and because my bandwidth keeps going up. I'm currently using 150+gb of bandwidth.
The first thing I noticed is the files are huge! I rekon if you spent a weekend (depending on your skill) doing a total re-design, you could make that site really fantastic and at least double your adsense earnings.
No one will pay for video game covers because they're available at a lot of places on the net. Your numbers aren't that high, but with Fastclick or one of the other ad networks (assuming you can get in) could probably get you $100-$150/month from impressions. I wouldn't count on clicks, especially via Adsense, as no one would go on your site looking to click/buy anyway. They just want what they want -- video game covers, and then they're gone. So I suggest getting into an ad network and make the impressions work for you. Run everything from banneres to pop underes because loyalty is not very high anyway with your field.