Regarding the "Upload Failed" message in SpeedGrader indicating that the DocViewer component of SpeedGrader cannot render/display a file type, it would be nice if an unsupported file type just displays a message saying that DocViewer cannot display the file type, and to download the file submitted by the student. This is documented in the SpeedGrader how to guide: https://community.canvaslms.com/docs/DOC-12774-415255021
I teach coding courses and this requires .zip file attachments that students submit online. So of course they have to be downloaded anyhow instead of rendered in DocViewer. Someone brand new to Canvas who teaches courses with this type of requirement might be concerned that their students' work got corrupted or altogether lost and spend wasteful time contacting support or telling their students that they need to resubmit their work. I also support other instructors and on more than one occasion they have mentioned to me this was of concern to them.
Here's my suggested reworking of the message (the red box is my emphasis):
I'm not sure what you would do for the kite in the tree graphic. I assume this is a Peanuts Charlie Brown Kite-Eating Tree reference which I'm not sure the current demographic always gets anymore.