What really validates your Certificate of Authenticity is your signature and you should
hand-sign the document. Then it is as legal and binding as any document you sign.
The form and look of your Certificate depend entirely on you. It may be simple, with just the necessary text, or you may add a decorative element, printed or hand-drawn too. Try not to make it too 'busy' visually though, remember that its main purpose is to guarantee that you are selling an authentic, unique work of art.
If you Google 'Certificate of Authenticity templates', many different designs will come up and you may get some inspiration there. I hope this helps
