There are several issues here.
Yes, it takes a little while for the new avatar to propagate through the servers BPL uses. Maybe an hour or two.
Your ISP may have your avatar photo cached and serve it to you from their cache rather than going back to the BPL servers. You have to get them to clean their cache. This can take hours – or days. If they do a restore they could conceivably revert.
Your own web browser may also have your old avatar held in cache, and cleaning that out can take time.
Try asking your browser to do a full refresh.
Cheers