Your site, in current setup, wouldn't last very long if you had hundreds of concurrent requests since you have so many requests. You do realize that most browsers allow two concurrent downloads per IP? You should distribute all these images across many subdomains (just make up subdomains; they can all point to the same server).
assets1.revzilla.com, assets2.revzilla.com etc.
Also, why aren't you running a real server for static content?! Mongrel ain't gonna cut it. Use Mongrel for dynamic stuff (i.e. Rails pages) and use Nginx (or apache or lighttpd) for static content (css and all these images that you have).
Finally, google for "css sprites" and optimize these images.
PS: Site looks good but it's just horribly assembled. You should replace 90% of those images by using CSS colors.