I have the same problem, my Trello account as an atlassian one (if I want to update my profile it says "This is an Atlassian account. Edit your personal information and visibility settings through your Atlassian profile.")
I have recently change my profile picture on atlassian, but Trello is still showing the old one.
I am afraid that if you are not using Atlassian Access, your Trello is not connected yet via SSO however it should work when using Cloud. If this is not working the way I can think of is to use Gravatar that might get automatically uploaded to various sites (including Trello that is supporting it)
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