Hello,
how I can change the icons design stile?
The custom ‘facebook’ icon is controlled by you, so you can point it to any image.
Replacing all the default icons is not easily doable, and I would recommend not to do it, as viewer updates can introduce new icons which will not work well with your customization. If you would like to try anyway, you can use this post as the starting point: Is it possible to add IDs to the SVGs in the help menu folder? - #4 by Wallenium