How do I add my icon/picture to messages on my Mac?

Hi Wendy,

Thanks for using Apple Support Communities. This article explains how to change your Messages picture:

Messages (Mountain Lion): Change pictures

http://support.apple.com/kb/PH12010

It is written for Mountain Lion but also applies to Mavericks (OS X 10.9).

Cheers,

- Ari

Changing the picture will be what you see, but someone receiving your message can over-ride your choice if they have a different picture in your contact card in their Contacts.