We have a few issues when new admin users try to change the logo in XWiki, as it can be seen by the usability tests and posts from the forums below:
Propose a way to improve the usability of thisprocess, taking into consideration what we already have.
https://design.xwiki.org/xwiki/bin/view/Proposal/IdeaChangeLogo
https://www.xwiki.org/xwiki/bin/view/Documentation/UserGuide/GettingStarted/ChangingTheLogoAndThePanels