Cavendish is a nice mediawiki theme with clean design, header navigation, 2 columns, rounded corners, left sidebar in delicate blue color. Mediawiki 1.6-1.7 compatible. If you are looking for stylish and elegant design for your mediawiki-driven website, there is no need to search something else, just stop at Cavendish.
Clean and Blue is today’s free mediawiki template. Its name says for itself. It is a clean and blue layout with 2 columns and left sidebar. Clean&Blue mediawiki theme is suitable for those who prefer simple and minimalistic design.
Free mediawiki skin presented today called SnapHouston was designed in yellow and white colors. It includes 2 columns, left sidebar, what else?…Well there is no need to go on describing, just look at it. It seems to me that it symbolizes sun, warm and summer 
Cosmo Chips is another free mediawiki template with a strange name It was adapted from the browser-side source of The Mono Project. Cosmo Chips mediawiki theme carries clean design, black, white & green colors, two columns and right sidebar. It can be an ideal design for your personal, single-user website. Download it and you won’t feel sorry.
