algent Thanks a lot! I tried a lot using lightdm-gtk-greeter and lightdm-gtk-greeter-settings but none of those worked. I was probably going wrong somewhere, but it was setting the login screen wallpaper back to the default Desktop Wallpaper (Pines.jpg in /usr/share/backgrounds/solus) instead of the one I had set. Pines.jpg wasn't even set as my Desktop Wallpaper.
Anyway, thanks a lot, once again.