MOE uses two rolling workbenches that were built in the robot lab by the team over several years. They have two overhead, removable shelving units. Dissassembled, the whole pit can fit in the back of a pickup truck for transport to events. One workbench is shown above. They have a built in vise and I think a drill press.
You can get Autodesk drawings and a ppt presentation on the design at
http://moe365.org/moepit.php
We don't like overhead ceilings or walls either - too limiting. And it's nice to be able to interact with your neighbors. We also don't really have room to display banners or large signs. But in addition to the workbenches there is a tall separate shelf to display info about the team and some small assorted boxes for parts. The setup can adapt to any size pit area.
We used to have a 25 (green of course) tower with a rotating light on top that was made from some scrap carpet stretchers a team member found. But now they have height limits, so it was cut down to 10 ft and now has an electronic message board on top and a clock.