You could use a centred background-image on a 100% wide div and then the div would just shrink as required without scrollbars. The div of course would need to be outside of any page containers. If the awning is the first thing on the page then just apply it to the background of the body element instead.
Regarding page width then that's a contentious issue these days as there is no perfect width and the best approach is a fluid width that accommodates all devices. If you absolutely must have a fixed with then 980px would be better than a 1000px as that allows for the chrome on 1024px systems and is also the measurement that the ipad bases its initial scaling on so would fit neatly.
With so many devices around these days you should be looking at responsive design. Do a search of this forum as there have been a number of recent threads about this.