So this is a great topic, and some very good ideas!
Here is what mine says:
Thank you for your purchase! I know you have many choices and appreciate you choosing Amy Davis Art. I will be shipping your package as quickly as possible. If you need it sent Priority or Express Mail, please convo me and let me know; I will look up pricing and send you a separate invoice for that through PayPal, and once paid I will ship. If this is a gift, I am happy to provide a note with your personalized message on it; again just convo me. I am happy to accommodate you in any way I can.
Thank you and God blessing you & yours,
Amy
It took me awhile to realize how this message worked, as I only had the first sentence when I first started, then realized I needed to add more. The message about the shipping was due to experience, lol! I like the idea of also putting my policies there, too.