If possible - don't place any images within the body of your page wider than:
538 pixels (liquid template)
600 pixels (fixed & other templates)
This doesn't mean that your content can't flow to widths larger - that's the idea of a liquid layout - but account for screens only able to fit 800x600.
We've targeted audiences with minimum screen sizes of 800x600... and content larger than that doesn't 'work.'