Where can I set a default Greeting and Signature for my emails?

You can specify a Greeting and Signature from My Account > Email Settings.

Both fields are open-text with formatting options. Newly generated emails will be pre-populated with a default greeting and signature if one is specified in settings.

There will also be a “Powered by ArtBinder” link in the bottom right of the composed email, which can be manually removed in the email composer if you wish.