It's a bit showy but I can't deny that I'm partial to a bit of translucency on the desktop. This patch for Mutter brings an opaque sheen to GTK apps.

This post, ‘Mutter Rounded’ Gives Apps a Translucent Blur Effect on Ubuntu is from OMG! Ubuntu!. Do not reproduce elsewhere without permission.

Want to change Ubuntu's login screen background? I walk through the steps for changing GDM background to a solid colour, gradient, or custom image.

This post, How to Change Ubuntu’s Login Screen Background is from OMG! Ubuntu!. Do not reproduce elsewhere without permission.