There is no simple button to do that.
You have 3 choices.
1) Learn how to design whole cart just by yourself using the tags.
2) Play just with CSS sheet. Single file witch allows you to change look of the pages.
3) Buy something ready. I saw couple of templates sold on few web sites. But in my case I just played with the CSS and used my own images. (I do not like anything offered out there.) Simplest solution used by many people as you can see in the existing shops sections.
How it looks you can check on santasshop.info
The hardest part would be probably for you to develop your own images to use. (If you have nothing to do with graphic design)
First i was trying to play with tags but having other things in mind than learning how to code I used the simplest for me route. CSS sheet. there is Rapid CSS editor I can reccomend.
I can also adjust the background color for you and e-mail you my CSS sheet. it would be the simplest way I can help you with.