One solution is to design an 800 pixel wide container for the website and horizontally center it; higher resolutions will see a margin on either side, which adds a nice little touch. A more complicated solution is to create a fluid design, one which changes depending on the viewer's resolution. This can be achieved either by scaling everything on the page or using scripts to present specifically designed pages.

As for bandwidth, I don't suggest tables if you intend on accomodating dialup users. Tables add quite a bit of dead weight to pages that will be quite noticable to dialup users. My suggestion is to design with CSS layers, which very much reduces to weight of your pages. As well, try using CSS classes instead of repeatedly defining elements inline.

Images can be nice, but they're often used unnecessarily. It's possible to design a website entirely with formatted text and make it look quite nice. I generally limit my images to logos and content such as artwork.