Manual:$wgInterwikiLogoOverride

Details
List of interwiki logos overrides. This is used by the sister project sidebar. This list accept a key equal to the interwiki ID (as defined in the interwiki links), and accept [ https://doc.wikimedia.org/codex/latest/icons/all-icons.html a Codex icon name] or a base URL for the given interwiki. Example: