My facebook profile image is not square (its. 500 x 400). Most Facebook profile images are not square.
When you upload a profile pic in FB you are asked to crop the photo - so when it is displayed in a square setting it is displayed correctly.
Perhaps there are multiple instances of the profile image saved on the FB servers? If so, please could the square image be pulled from FB and not the original image? Why?
Currently the plugin pulls the main image which is squashed/distorted into a square crop. If you do not have a square image it looks poor and I imagine most people will not have a square image.
Any questions do let me know.
Seems like this is a relevant thread here: https://premium.wpmudev.org/forums/topic/increase-size-of-fb-profile-image#post-228039
@Vladislav @brad_paterson @Arun Basil Lal