Replacing an old image on the PirateCraft wiki can be done through the “upload file” button on the left hand bar. It’s possible to upload a new picture, but you can’t change which picture is selected to be displayed. Does the forum admin have the secret permissions to do something about this?
Example: I wanted to make a new government chart for my crew’s wiki page, but I realised that Edori_an’s name had an annoying autocorrect line underneath it. So I obviously tried to upload a new, clean image. The new one I uploaded didn’t push the original file down the list, however, so the picture doesn’t change. I also cannot see any option to select which picture you want.
http://wiki.piratemc.com/File:PC_BE_Government_Spring_2016.png