One should take care that key details are not cropped.
The first image in this post contains a cropped picture of my great-grandfather, Fred Ufkes.
It turns out in the background, very faint, is the church which was a few miles from their home.
If I had not already suspected where the picture was taken that church would have been a big clue.
Your archival scan of a picture should include the entire original image.
There could be clues hiding in what appears to be "background."
It is difficult to see, but the church is there. I think it's the only clue in the background of this image, but it I had gotten "crop happy," I might have cut out the image entirely.
In some cases there may be clues that allow the researcher to more precisely date the picture as well.
Pictures taken in urban outdoor settings frequently have environmental clues, but rural pictures can as well.
Don't cut out clues--save the cropping for later.
[note: pictures were shrunk for this post as I'm close to using all my Google space.]