Customising a category design

Hi, I want to change the layout design on the template Core 3.3.1, at the moment it looks like this;

http://tubebackgrounds.co.uk/category/gaming-youtube-backgrounds/

How can I change it so it shows the images? If possible, shows the text on the left hand side, and the picture on the right. (I’m pretty proficient with CSS so you give me technical advice)

Thanks.