Hello Nick,
There should not be an issue displaying images in tandem with choices based off of a cascading select. Are you seeing the same results in all clients? (Windows/Desktop field app, mobile field app, etc..)? Can you attempt to download the attached example XLSForm and media folder and create a survey on your end using Survey123 Connect?
If it does not work on your end, we can explore reasons why that might be the case in your environment. If it does work, please take a look at what may be different in your XLSForm compared to what is in the one attached. Also, in that case, it may be helpful if you are able to upload your survey and media folder or send it to me in a private message.
Brandon