I didn't see anything in the source code.
It isn't that it cannot be done, just that it will require putting the image into a text widget and then using CSS to move that up where you want it and adjusting the positioning of everything else to get it out of the way.
900px wide x 500px tall is a really, really large image and is going to push any content down completely out of site for visitors on normal monitor resolutions. Not the best thing from a web design standpoint unless that image is the whole focus of the site and the rest of the content is just secondary babble.
Or is the image 900px tall x 500px wide? That would actually be way worse.
At any rate if you want to do this, upload the image, put it into a text widget in the sidebar and then I'll work with it later. I'll just home for a short bit and then gone again for probably 4 hours.