I have the same problem. When I updated the screen went above and below outside of the viewing area. I posted in August http://pimame.org/forum/discussion/1237/top-and-bottom-of-display-screen-cut-off-after-update#Item_4 and tried what they recommended but it didn't work. Hopefully someone can help us!

we are working on building a database that will give you not only images, but also game descriptions, ratings, number of players, developer/publisher info, so I made the images smaller in anticipation for all of this extra info. Once I figure exactly how the layout will be, the images will probably see a resize. Right now, you can mess around with your theme.yaml file to get bigger images. The image size is based on the screen width minus the width of the game titles. so if you make those smaller, the images should get bigger. I think that there is a couple other things that you can tweak in there to get a little larger image.