The repetitive nature of the same airlines and the same types is what you expect of airports these days. Every once in a while, though, the airlines put some extra decoration on their aircraft. Usually you can see that there is something there before you get to see what it actually says. JetBlue have an Airbus A321 that is apparently their 200th aircraft. It has a big decal on the rear fuselage to highlight this fact. It apparently joined them over a year ago so a bit late for congratulations.