To display thumbnail images of the product in the cart, set the appconfig parameter ShowPicsInCart to true.
To rearrange the shopping cart headers, or to add additional headers, you'll need the source code, and you'll need to modify the ShoppingCart class (ShoppingCart.cs) in the AspDotNetStorefrontCore project, then recompile and deploy the new AspDotNetStorefrontCore.dll assembly to your site.
For styling issues, the best tool in the arsenal is Firebug (add-on for Mozilla Firefox browser). If you don't have it, grab a copy of it (it's free) and you can view all css styles that apply to a particular page when the page loads, and can even adjust styles within Firebug that will apply to the page in real time. You can determine which styles you need to change to get it to look the way you want, and then can make the necessary changes in the actual stylesheet.
<a href="http://www.aspdotnetstorefront.com">Shopping Cart Software</a>