Using facebook graph api get News feed: https://graph.facebook.com/me/home?access_token=...
The picture field it returns is all in smallest size, like picture\": \"h
Along with picture field, there is an object_id field. Put this id in below url:
https://graph.facebook.com/{object_id}/picture
This will return actual size image. Or you can write this for different image sizes.
https://graph.facebook.com/{object_id}/picture?type=normal
Where type can be : thumbnail, normal, album.