Thanks for the responses. While I love vintage cars and bikes, I know nothing about the bikes!
Well, after a quick look at the family tree, my Grandma was born in 1898, and was married in 1925. I'm sure this was taken before she was married, so it must have been the early 20s. The picture I posted is zoomed in, as there are two more bikes in the shot. It's quite a small photo, only postcard-sized.