What about using NIP-94 to check that the profile picture is not changing while still using a HTTP URL to get the file?
Kind-0 attribute could be added to publish the profile picture this way, innit?
Discussion
There are two ways: you can do another field in the User Metadata for NIP-94 that will store the nostr:nevent OR add a URL suffix like "#nip94=nevent"
Either way, you need client support to change your image correctly, and client support to display the nevent field and the verify the image.
Pixel and HTTP ping tracking would still happen, though.
Yes, tracking will still happen if no proxy is used, but the picture will be change-protected in nostr clients supporting NIP-94.
I think it's a step in the right direction.
And less controversial that NIP-95 right now.