Go to the profile.
Click on the images tab
Click on the photo that you want to remove.
Scroll down. On the left hand side about the middle of the page
People & Things in the Image:
Click on the little round button in front of remove from image.
Then scroll Down to SAVE CHANGES TO IMAGE DETAILS and click.
This will send your photo into limbo for about 3 weeks and eventually it will get deleted from the wikitree server.
You can then upload a new one, or you can do this first.
