All of the photos on the cover of Ben Yandell's book The Honors Class appear in the book, except the one in the upper left. I'd wager a beer that the mathematician in the upper left corner is A.N. Kolmogorov, but I'm not 100% certain. Anyone know for sure? Yandell died in 2004, so I can't ask him. I did a google search on Kolmogorov, and the photos shown are consistent with my guess, but none are identical.
There's a photo on the back of Busemann which isn't in the book, but the photo of Busemann which is in the book leaves little doubt that both photos are Busemann.