That just a placeholder.
If the user set the profile picture and banner empty that this image shows.
If the user set the image incorrectly that the picture will became black or other thing.
If the user set it correctly that just wait the profile fully loaded and u will see the true images.
But if u net is not fast enough that this image will shown when client loading the detail of the profile.
I hope this helps.
**AnonymHe on 23/02/09 02:31 (UTC+8)**