You might have noticed that when you install a new third party app on your elementary OS the icon will be different style than the ones whist the default apps have. It’s because elementary’s default icon set is limited to applications installed on the OS by default. That’s why elementaryPlus, a.k.a elementary+ Icon Theme was created.
It adds numerous indicator and application icons on top of the default elementary icon set so third party apps will fit into elementary’s design.
How to install elementaryPlus
There1s a eprfect installation guide at elementaryPlus’ Github page, so I just copy it here.
You can add our PPA (Personal Package Archive) to your sources:
sudo add-apt-repository ppa:cybre/elementaryplus
sudo apt-get update
sudo apt-get upgrade && sudo apt-get install elementaryplus
or just download or clone this repository.
To enable the theme, launch “elementary+ Configurator” from the application menu or run./install.sh from the parent directory of this repository, respectively, and switch on the “Core Icon Theme” option.
Please also make sure, that the original elementary icon theme is installed, because elementary+ only provides additions and inherits the base theme.
The elementary+ Configurator
More info: https://github.com/mank319/elementaryPlus