Hello,

This is a manual process unfortunately. The reporting is done by persons who deem the photo inappropriate, but I find students do it because they like to click links.

I have a set task in outlook that repeats every Monday to remind to check the profile picture report. If the picture is fine, I approve it. If it's inappropriate, I delete it.

Once I caught up (when I found the feature), there are usually not but a few to do each week (100K+ users in our district). 

If you find a user is repeatedly uploading an inappropriate picture, you can delete and then lock it so they can't upload any longer.

https://community.canvaslms.com/t5/Admin-Guide/How-do-I-manage-profile-pictures-for-users-in-an-acco...

This just isn't a well advertised needed admin process (in that I found it by complete accident).

Cheers,

Chad Scott
Katy ISD