I have a design business in the UK and we sell products as well (Traditional Hand-drawn Map of London (wellingtonstravel.com)). However since we sell it ourselves on our website using paypal there's no way to get social proof from our customers.
If we sold on Amazon, eBay, or had a physical address (Yelp or Google Places), we could gather 3rd party reviews. But we don't, so I'm looking for a way to demonstrate our excellent track record. Any ideas or suggestions?
This seems to be a problem faced by other designers too. For example: florianpucher - Carpet Design (florianpucher.com)
http://www.quora.com/Customer-Feedback/Where-can-customers-leave-feedback-for-my-business