Facebook has lifted many of the restrictions regarding cover photos. Cover photos can now include calls to action, price and purchase information, contact information and Facebook references (such as “Like”).
The arbitrary 20% text rule is still in effect – cover images cannot be made up of more that 20% text.
Some people have found this rule confusing, but now there’s an easy tool to see if your cover photo violates this rule. You simply type in your Facebook page URL, wait for it to populate your cover photo, click on the areas of the photo that include text and wait for it to give you your text percentage.
Check out the Facebook Cover Compliance Tool.