PeerTube admins,
You can now very easily customise your PeerTube website to have your own logos, banners, icons, headers, default theme (including dark/light defaults), colours, menu styles, extra themes, CSS tweaks etc.
All of this is in the GUI, no need for coding!
Log into your site with your admin account, then go to:
Settings > Logo (for logos, icons, banners)
Settings > Plugins/Themes > Search Themes (for extra themes)
Settings > Customisation (for everything else)