If you put the entire content of your message in the images, I'm not going to see them. I have remote image-load turned off, and I'm not going to turn it on because I know you track people that way.
Sure, tracking is useful to know who has read your message -- but you have to earn that right by convincing me that you're a good company who isn't going to deliberately misuse that information. Most companies aren't.
Also, I just prefer the information to be in text anyway. Tell me what it is you want me to do, and why I should want to do it; don't try to lure me with bright colors.
I guess this makes me atypical and probably not who you're marketing to anyway.
But still. Put your message in text, or (at least) in attched images, or I won't see it.