Both square and rectangular "head shots" of faculty are used in CCB's web site, and they may all be different for any specific faculty member. And VIVO's square photo may be different from all of those in CCB's web site!
Rectangular photo required
255 wide* 170 high (landscape portraits)
If square or otherwise a different aspect ratio, it will works, but it won't look as nice:
Square (115*115) example:
http://chemistry.cornell.edu/faculty/detail.cfm?netid=ggh4
Portrait (not landscape) example:
Square photo required
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Example when a rectangular photo is used where a square one is intended:
http://vivo.cornell.edu/display/ya222
Variety of professional looks:
Yimon Aye's photos are very different from each other: