Make administration categories images expand horizontally, rather than vertically

In the initial Administration proposal, the images were expanded vertically
http://incubator.myxwiki.org/xwiki/bin/download/Improvements/Administration/categoryView.png

The problem is with large displays: there is lot of white / unused space in the right of the screen.
Also with the current format the user is forced to scroll down in order to see all the entries, and this case is specially important for the Applications category.