Hi Susie,
This might work for you if I'm understanding what your client wants. The "susie.jpg" is 2000px wide by 800px high and absolutely awful, I just threw it together to try it out. I'm not sure what the biggest monitor width size would be. I have dual monitors at 1280px wide each and I dragged the browser window across both screens to get the right hand side to go to full limit with the content staying in the middle. I only tested in Firefox (Mac)
You can see it here
http://180virtual.com/susie/