What is the best way to edit the front-end design of the category page? I would like to add some extra banners/colors etc but I can't really find the best way to do this.
I do not know if I understand you correctly. But if you want to add some group/category related things to the to of the product list, you simply need to go to the product list page -> Visual Editor. Then drag in an empty row, and then one of these column types: