My uploaded picture shows on all sites except Meta SE. I haven't set a different one here, it just shows the default picture. Seems to be a bug?
I solved this by editing my profile on a site where my picture was showing OK. In the dropdown, I deselected my uploaded picture, then reselected it, and on save I chose the option to send the update to all sites. It now shows here too.
So if it is a bug, that action seems to be effective as a workaround anyway.