All images and links on a site should work. Spelling should be checked and re-checked by hand.
Nothing is as unprofessional looking as a site with spelling mistakes.
Web site design should be consistent thoughout the site. Different backgrounds or different navigation only serves to confuse the visitor. The more you update your site, the more visitors you will receive. Changes should be made at least once a month, even it if is only changing out an image or lines of text. It depends on what kind of audience you are trying to reach.