The difference between the US version of the TIME cover and that of the rest of the world recently proved to be a popular comparison on Reddit, with some calling it censorship.
Selective variations might appear politically-driven, but might it be the result of the publisher attempting to increase sales in different markets? TIME is supposedly the world's largest weekly news magazine. Why wouldn't the company change cover depending on what it thinks will sell?
The above examples mightn't look great in isolation, but you don't need to venture far into the TIME archives for differences that aren't as noteworthy.