Follow these steps to style your Ubuntu distro using the Arc theme like the picture below.
sudo apt updateOpen a browser and go to this URL to download the image. Put the image in the Pictures folder of your home directory and rename it to background.jpg.
Put your desired profile picture in the Pictures folder of your home directory and rename it to profile.jpg.
sudo apt install arc-themesudo apt install pocillo-icon-themesudo apt install gnome-tweak-toolTo disable mouse acceleration, launch Gnome Tweaks, go to the Keyboard & Mouse tab and set Acceleration Profile to Flat.
sudo apt install gnome-shell-extensionsLog out and log back in to reload the GNOME shell. Launch GNOME Tweaks, go to the Extensions tab, enable User Themes, relaunch GNOME Tweaks, go to the Appearance tab and select the Arc-Dark shell theme. Set the Applications theme to Arc-Dark and the Icons theme to Pocillo. Select the background.jpg image in the Pictures folder of your home directory for both the Background Image and the Lock Screen Image. Go to the Top Bar tab and enable Clock Date. Launch the computer settings, go to the Users tab and select the profile.jpg image in the Pictures folder of your home directory.
sudo apt install screenfetchThe screenfetch command should display WM Theme: Arc-Dark, GTK Theme: Arc-Dark [GTK2/3] and Icon Theme: Pocillo.
To use more readable colors for the dark terminal theme, launch Terminal, click the Terminal menu in the top bar, select the Preferences menu item, go to the tab with the current used profile, go to the Colors tab and select the Solarized palette.
Ubuntu 18.04:
Open /usr/share/gnome-shell/theme/gdm3.css and edit #lockDialogGroup by commenting out the existing background style and adding background-color: #383c46;. A reboot might be required for these changes to take effect.
Ubuntu 20.04: See this repo.