We were trying to upload the images instead of just referencing them with fmap. There was some confusion between the two on our end. German walked me through setting up a custom configuration for storing images as well. Thanks for the help everyone!

This document appears to refer to changing the appearance of the UI, not placing images on dashboards. If they're only mentioning the two file types though I can see how that would suggest others aren't allowed. I don't think this is conclusive but it is helpful. Thank you.