Thanks to Cooper Miller for sharing this idea.
"Facebook recently updated their groups allowing you to add a cover photo. It's fun to put picture of your club or campaigners in there but also cool to use it for a banner. It adds personality and professionalism to your Facebook group! Here is one I made for our campaigners page that you can right click on and save to use."
Here is a link to a downloadable file that you can edit to make your own facebook group banner.
Here is a link to the font you should use.