Assign images to non-DC users?

Hello :wave:,
I’m trying to find a workaround to assign a profile picture to non-DC users.
Does anyone know if it is possible to name an image file in the backup so that that DC interprets it as a profile picture for a contact? Maybe through an additional change in the SQLite database?
While trying out various options, I noticed that DC does not accept self-created TAR archives as backup. Not even if the content is completely identical to the original. Does DC require a special TAR format? I use Keka to create TAR archives.