Wider image

The default image is 722 px wide and 12 px tall. I have created one 822px wide which should allow a main post 100 px wider.

Your default outerwrapper is 692 px. Your post width is 400 px and your sidebar width doesn't seem to be defined. There may be some padding I have not accounted for.

Here is my wider background. Click to see image full size. Downloading the blooger version seems to match the version I uploaded. It is a gif file.