Great tips and topic, D-Jam. Thanks!
I would add that it’s important to keep in mind the differences between the horizontal “cover” image as displayed in Facebook personal or DJ pages vs. the event pages. I imagine the one you posted is for an event page.
As you guys know, on pages we have to consider the presence of the “profile” picture on the lower right corner, while on event pages we have to consider the presence of the smaller thumbnail image displaying the event date.
Two other issues are how these pages are displayed on mobile phones vs. computers, and how event cover images will show up on the Facebook Events List and on Facebook adverts (I’ve used paid Facebook ads to promote events with very positive results).
So we should always review these two sets of Facebook guidelines before designing our cover images:
Facebook PAGES => https://www.facebook.com/help/125379114252045
Facebook EVENTS => https://www.facebook.com/events/336235416488540