Why not just do the images as embedded from your website? I send out this type all the time and it works well.. As an added bonus you can see how many emails are opened by looking at the hits on the files from the web server. Just make sure you know how to do slices so that the images are easy to download and read.
This also cuts the delivery time greatly - there are no files to send.
Lloyd F. Tennison email@example.com
No trees were harmed in the transmission of this message. However, a rather large number of electrons were temporarily inconvenienced.