Hello,
I don't think this is so much a "bulk email module" issue, but, unfortunately, more of an "HTML email standards suck" issue.
When writing an HTML email, you have to write it a bit like you are writing a website in 1997. You should assume that images won't load and style things need to generally be done in-line. Also, you should use tables for layouts. You can find out more about this here:
http://www.campaignmonitor.com/design...
The images generally don't load because of security issues. Emails don't carry images in them normally; instead, they are stored on the server. In a browser, this is fine because the server already knows you're there from the page request. With email, malicious users could track your request for images and use that to determine if an email was read. This would tell spammers about whether an email address is live. This vulnerability is countered by blocking outside image requests in most email programs.
As a email designer, you need to assume images will be blocked (at least initially), and design your communications to still look decent and render properly.
Hope this helps,
Mike