Small graphics should be no more than 1-5k in size. Repeat graphics when possible. Remember that people may not be able to see the graphic. Always provide a text version of the graphic, so people know what they're missing. If the graphic is to be used as a link, ensure that a text link is also available.
Image maps can be very useful additions to a page.
However, remember that they can take a long time to load, and you should have a text link as well. You can repeat a link to the same page many times at the site. For example, to back to the opening page. If graphical, make sure there is a text equivalent, if textual, ensure there is some context to the link. Arrangement of links.