There are quite a lot of pictures on the database corbis.com, and with a bit of luck, one can find some interesting ballet ones...
For example, typing "Royal Danish Ballet" leads to about 15 old black and white pictures of performances in the 50s (plus a photo of Erik Bruhn).
There are several Balanchine-related pictures, including the one: http://search.corbis.com/default.asp?q=HU0...&v=1&s=HU005728
It's supposed to be George Balanchine and Margot Fonteyn in 1950 in London (is it really Fonteyn? I don't recognize her on that photograph...)
Also there is a photo of him instructing a ballerina in Copenhagen (date not given), at:
http://search.corbis.com/default.asp?s=bal...a=3&p=2&r=9&m=1
(picture ID BE031545)
Does anybody know who that ballerina was, and can you recognize the ballet?
The pictures are quite small, and sometimes the legends are very unprecise (dancers not credited, etc.), but trying to find ballet photographs and to identify which dancers or ballets were photographed can be an amusing game on my opinion.
A few other photographs: http://search.corbis.com/default.asp?s=bal...a=3&p=9&r=9&m=1
Title "David Blair copies ballet postion" (sic), Sept 8, 1950. The man in the middle is Balanchine, but who is the ballerina?
http://search.corbis.com/default.asp?s=bal...=3&p=13&r=9&m=1
A nice photograph of Tallchief and Skibine in "Concerto Barocco" in 1948.
http://search.corbis.com/default.asp?s=bal...=3&p=11&r=9&m=1
Yvonne Mounsey and Francisco Moncion in "The prodigal son" in 1950.
http://search.corbis.com/default.asp?s=bal...=3&p=12&r=9&m=1
The legend is really odd:
"Russian ballerina Lubov Tchernicheva portrays Cleopatra in the Balanchine ballet Ceasar and Cleopatra. Ca. 1920."
http://search.corbis.com/default.asp?s=lif...a=3&p=1&r=9&m=1
Tchernitcheva, Lifar, Danilova and Massine in Massine's "Le pas d'acier"
(There are quite a lot of pictures of Danilova: in "Coppelia", "La boutique fantasque", "Le Bal", "Giselle", "Apollo"...)
People are welcome to post the URLs or photos IDs of the photos they find interesting.