Relationship
Every business should strive to build a relationship with their customers. Even after the purchase has been made we still need to engage with our customers, this could be in the form of a survey form or a thank you note. People would appreciate a survey form because this means you care and that you are listening to them.
Video application
This could be a video saying thank you to your customers. It can be animated, or it can be a real footage of you saying a thank you message. Some might see this as unnecessary but sometimes going the extra mile to show you care, would go a long way.