We can brand/skin the storefront on a store by store basis.
This can be as simple as changing the logo on the out of the box XMPie solution or a complete redesign to match a customers current brand guidelines. Depending on the complexity will determine the time and skill set required to acheive the desired result.
A familiarity of HTML and Cascading Style Sheets (CSS) is beneficial to acheive these tasks.
Like designing a print document, the process is very subjective but by breaking it down into smaller elements it does not need to be a complex task.