Special:Allmessages has a page for it.
To change the welcome message in Message Wall, edit in MediaWiki:Welcome-message-wall-user. To change the welcome message in talk page, edit in MediaWiki:Welcome-message-user.
Sorry I may have explained it wrong. I mean't like everyone you go to a new wiki there's a "Welcome to (Wiki name) wiki". How do you change it since apperently in a wiki that I am an admin in, the welcome message for all users is weird since that person is no longer admin, however people are still recieving messages from him.
It is very hard to help, if you don't give a link to the wiki you're talking about. We're not psychic.
Okay then here
On your main page is the following code:
<div style="text-align: center; font-size: x-large; padding: 1em;">'''Welcome to the {{SITENAME}}!'''</div>
So, as you can see the magic word {{SITENAME}}
is what decides the name of the site displayed. This was set when the wiki was created. You need to ask FANDOM staff to change the name... what did you want it to say that is different?
I believe RealArgoFox is talking about message like this. Is that correct? If so, than UpnCbs06 and Applemasterexpert were on the right track, RealArgoFox just didn't understand their replies. I suggest reading Help:Welcome_tool as it will help clarify the replies.