"I have to say I am very impressed with the work you have done on my wall.
Several people (strangers and friends alike) have said how well the work looks, and how they have noted your attention to detail and the quality of your efforts.
Do you have an advertising board with your contact details? If not, then I think that you should! Also, do you have any business cards? I am quite willing to have a contact details board outside while you are working on my house, and also very happy to hold/give out business cards to anyone interested."