Really, the ideal way to brand Foodclub with your own logo is to design your own UI theme. All a theme is is a single CSS file, as you can see if you look at the HTML source when using the "ncfc" theme (default), which is all contained in
http://foodclub.org/css/themes/ncfc.css.
So if you want to design your own, you can simply start adding CSS in your global CSS styles (
Global settings), which will apply (cascade) after the ncfc styles, until you like it. If you end up with something different/unique enough, a new theme can be created for you (and other clubs to use, minus your logo of course).
As for using your own logo in the "ncfc" theme, the white space near the top left, just above the green nav bar was designed for a logo. You can reference your logo by URL (hosted on another site) using CSS to place it right there. I will add some sample CSS to this topic shortly that shows how to do that.