On a whim I did a quick search and found this neat tool
that will help you build an image map from your image. I tested and it worked quite nicely. I put the code that was produced in place of %logo.
The process I would use is upload your logo which you have already done and then use the URL to that image in the image map tool. The code that is produces will be ready to paste in. You may have to fiddle with the CSS a bit for positioning.
I'm glad you asked the question as this was something I had been wanting to look into for some time but keep forgetting.