Using non-standard HTML constructs that are vendor specific or vendor exclusive potentially communicates a condescending arrogance to the visitor. Change the picture on the homepage regularly to breakup monotony. Spred information out a bit and have some whitespace. Have uniformity in the top levels, but allow individual departments flexibility. It is recommended that the department maintains uniformity within the department.
Image maps can be a real problem.
Adds to page clutter and loading speed. If done improperly, the user has no options while the page loads. To update is time consuming and requires well written documention for multiple maintainers. For example, If I have a beautiful navigation bar that needs updating, I have to know the graphics packages, font types, colors, and re-map coordinates to install or deinstall a new option. An alternative is to use tables, small graphic buttons, and the proper use of the ALT construct.