Embed Images

Yes, see Function Reference/wp mail

$attachments
(string or array) (optional) Files to attach: a single filename, an array of filenames, or a newline-delimited string list of multiple filenames. (advanced)
Default: Empty

Let me know if the upper method should work

No it won’t. Postman doesn’t use PHPMailer.

This should work: https://stackoverflow.com/questions/13135200/how-to-send-an-attachment-mail-using-wp-mail-mail

Postman uses an inline image in its Test Email. It’s done with CSS in an HTML body to an external graphic on the web.