I often get emails with huge images of really great art and design, that totally get the message across, except...
HTML emails are cool, but you've got to earn my images enabled trust. And if I'm reading your email on my phone, forget it.
If there is something -- usually anything -- to suggest I might like the images, I will enable them. So entice me (by using this code!)
Give it a try: http://pmnewell.com/eip/
(even with images blocked)
Huge tip of the cap to Email on Acid for their Mozify tool which inspired this in the first place. These guys are email geniuses.