Joomla 1.5 site - Split Categories

Hello, i have a list of categories in a joomla 1.5 site. I need to Split categories list in 3 colums (now it is 1 long column) and give ability to add a thumbnail for each category. This is allready done in another section of my site, so maybe you can get that code or do something similar... No need to manipulate Database because there is an add file to category.