My recommendation is the Metro Studio Sync Fusion desktop app.
Download the app by signing up for a free account at Syncfusion. You would be presented with a big number of categorised icons.
Easy way to search for the right icon is the quick search.
Your users don’t need to install or even know about setuptools in order to use them, and you don’t have to include the entire setuptools package in your distributions.
The conventional way to update Retro Pie and install new features is through the setup script.