Shopify is well known for having beautifully designed themes. You can view all the available themes in the Shopify Theme Store.
There are a number of themes you can choose from, some are free and some you are charged a fee. All of the themes currently available from Shopify are responsive too, which means they adapt according to the device being used to view your site, for example, a smartphone or tablet. You also have full access to edit the templates, enabling you to make any customisations as you need to.