At login you have this Ubuntu icon click on it and you have others options one off that is Gnome.
Gnome let you use extensions that extensions help you to customise the filling of your desktop, the best is to be able to install themes, this is what I deed to my system with some screenshots, open software centre and look for Gnome tweak tool, the return search is Advanced settings I installed that to see if is the tweak tool, before I start doing something I have open a browser and typed https://extensions.gnome.org/
once there you have this two tabs extensions and installed extencions, so my installed extensions as empty, on extensions page you have 20 pages of extension but the one I need as the user themes, you have this slider on/off moving the slider installs that extension on your system, to make my system more user friendly for my partner some extra extensions, like Alternative status menu, to have the power off link under my user name, this is hidden by default "ALT key will change from suspend to power off" and Axe menu. To finish of the changes I need some themes and a nice icon theme, again open my browser an typed http://gnome-look.org/, there is loads of themes to choose from, the themes I have install as eOS, Faience and MinimaZero, icon theme Faenza.
Thanks for reading this post.