Same probelm here. The Xfinity website is difficult to use as well.
I just noticed this as well. The images display fine on my phone using Chrome or the Xfinity App. Only issue is using Chrome on my laptop.
ComcastGabriel replied in another thread that this is a Chrome problem and one should contact the sender to have them use secure transmission means. OK - I am experiencing the same problem, i.e. images not loading - on email from COMCAST itself!
It seems that Comcast's web browser email service, with this issue, difficulties in cutting and pasting contact, delays of up to a minute for send email to transmit, and others, is going backwards.