I'm not even sure if this is possible but there is a profile picture in iTunes 12 that just has a default user icon showing and it's really bugging me. See below:
Is there any way to change this to an actual profile picture?
Simply put: No, you can not change it.
This is because Apple has designed it that way, and the only way of doing it would be going into the iTunes files, and if you're lucky and find an uncompressed image and just changing that one.
Otherwise, sorry but it isn't possible.