If you’re running Linux Mint on a computer used by more than one person, then you’ll be happy to know that it’s easy to change every aspect of the login screen, from what buttons appear, to the order that the names (if any) appear, to the background image, and more.
To start, you first should check out the themes for Login Screens that come with Mint, since there are many good ones right out of the box. To do that, just click on: Menu -> System Settings -> Login Window.
If you find one that’s close, but not quite what you were after, then you can copy that theme from /usr/share/mdm/html-themes/ to a subdirectory in your Home.
Now that you’re editing your own copy of the theme, you can modify the theme.info file to reflect it’s your own info. Then, tweak index.html & theme.css to taste. They’re usually pretty well commented, so you should be able to see what you’re looking to modify if you read through these files. Of course, now that you’re working on a copy of that theme, you can also replace the existing images with ones you prefer. (I like to keep them the exact same size as their replacements to make the change as bug-free as possible.)
For example, I was setting up a machine for a kid and so in my case, I liked the “Synergy” theme a lot, but I wanted to make a few small tweaks, so I copied it, and in index.html, I edited line 10 to force my kid’s name be the default username, and then at the end, in the <body> section (around line 331) I commented out the entire <UL> so he couldn’t mess around with any of the default buttons for changing language, putting the machine to sleep, etc. I also commented-out the Welcome message instruction a few lines below that, to keep the login screen as clean and simple as possible.
When you’re done making your changes, go up a directory, and then right-click the subdirectory containing your theme’s files & folders, and choose “Compress…” then accept the defaults and click OK.
Now, head back over to the Login Window Preferences in System Settings, and click the “+” icon at the upper-right to add a new theme. Select your compressed file and you’re done!
As long as you have some basic HTML knowledge this couldn’t be easier, once you know where to look!