Update: I guess I'm not familiar with Connect Text as I don't have Xfinity Voice. My previous comments, if anyone saw them, were related to Xfinity Connect email....
Maybe someone using Xfinity Voice or a Comcast agent will respond.
Update again: Chatted with an agent who researched and found that NO, the Xfinity Voice Connect Text does NOT support sending/receiving images. She took the request and said she was passing the info on to the app team.
As found in content of https://www.xfinity.com/support/articles/text-messaging-top-tips
Xfinity Connect Text uses the American standard "SMS" format for text messaging. SMS is perfect for sending text messages via mobile devices, because it is small, lightweight, and works on nearly all phones, regardless of the phone company or the phone's developer (Google, Apple, Samsung, etc.). To remain compatible with as many devices and phone companies as possible, SMS is limited to delivering text and emojis. For delivering photos and other file types via the web, we recommend using Xfinity Connect Email.