I would change the font too. I would use Verdana 12. Where there are thumbnails you are loading the full image. People with slow connection will certainly have problems. Such habit also pixelates the image and makes its content less neat. Using small thumbnails will also save you bandwidth, if that is a major problem, given that person will only load the large image if he or she likes the miniature.
You could change the colours to get a cleaner and neater design. For example:
1. Use a darker background;
2. Make that gradient shorter. Drop shadow filter used to obtain beatiful results when you use white mass over mid-tone and dark colours.
3. A simple texture for the dark background is very suitable as well.
That is just how I would do it, though.
I had not time to evaluate the navigation yet. But everything looks goods o far. Your engine looks very good as well.