I need some design advice

My site, the one in my signature, is doing really well in terms of growth, usability, interactivity, traffic, etc. However, I simply get sick of looking at it sometimes, since it is just SO plain.

I try to put myself in the position of someone who has never visited my site before, and I wonder if they would have any idea what the site even is.

What do you think I can do to improve the design? Maybe some images under navbar that explain the site (similar to infobarrel)? Should I place the "latest submissions" in a widget style box on the homepage? Maybe I should incorporate a colorful image for the background of the site, and make the page "scroll" free except on search and content pages? What do you think? I don't want to do anything that is going to use a lot of space or affect my loading speed too much.

I am working on some code that is going to make sharing info, in my opinion, different than any other site. The submission process and layout are the only things my site still has in common with other pligg-based sites, and aside from that, I have built and incorporated several features that no one else using pligg (that I'm aware of) has. Now I just need a nice layout, but have no idea where to begin!