I have just spent the better part of my morning looking for the logon screen ... the one that's presented to users as they are logging in... I have one... I see it... but for the life of me I cannot find it...
If you mean the Mystic logo, then its preuser.* file(s) in the default theme's text directory:
<root mystic directory>\themes\default\text
This is set by the very first prompt in the prompt editor for the default theme. You'll see in prompt #1 it has:
"|DFpreuser|Enter your user name:"
This tells Mystic to display "preuser" from the theme's text directory.
... If at first you don't succeed, blame your parents!
--- Mystic BBS v1.12 A48 (Windows/64)
* Origin: Sector 7 * Mystic WHQ (1:129/215)