The primary cover for March 6's Justice League #19 has been replaced with a new illustration by series artist (and sometimes co-writer) Jorge Jimenez. Because this change was made after the deadline for retailers to submit orders, the issue will be made returnable for retailers.
The original Justice League #19 was the first in a three-part triptych to continue onto #20 and #21. #19's old cover and #21's cover will now be variants to #20, with the centerpiece to be used as the main cover of that March 20 issue.
Because of this, a new cover for Justice League #21 is also forthcoming, but as yet unrevealed.