For your own personal e-mail, you can send HTML formatting, and link to the images remotely. Because of spammers using 'web bugs' and the like to track if their e-mail was going through, many e-mail programs have options to not load images, so if you're sending it to other people, it may not be rendered as you might have hoped. If you're just sending images, and not trying to send a formatted message that includes images, just send them as a MIME attachment, and most modern e-mail readers will handle it.

In the off chance that you are trying to send a richly formatted message that includes images, then follow zentara's directions. (I've never done it, but that looks like how some of the spam that I get is formatted)