Whenever I start Ubuntu there is always the default purple background that then fades to my custom desktop background. How do I remove/change it?
If you want your login greeter wallpaper to match your user wallpaper:
Copy your desired wallpaper into
/usr/share/backgrounds(make sure it's readable by "other")
Open dconf-editor and go to
com > canonical > desktop > unity-greeter
backgroundentry to the path of your desired wallpaper:
/usr/share/backgrounds/[your desired wallpaper]
Next time you logout and log back in, you should see your desired wallpaper on the login screen.