You can change the look and layout of your Mediawiki site. The place to start is the wikimedia groups' meta pages.
There is the [[http://meta:.wikimedia.org/wiki/Layout_design_document|design document]]and the [[http://meta:.wikimedia.org/wiki/Skins|info on skins]]or just dive into all the [[http://meta:.wikimedia.org/wiki/Gallery_of_user_styles|examples of user styles]]