Avatar vs Profile Picture vs Display Picture

I have noticed that on message boards, that we use the name avatar for the picture on our profiles. On Facebook and Twitter they are called profile pictures, and on Skype it is called Display Picture.

I know, in general, everyone should know the word avatar if you make an online profile before the recent change to Profile Picture.

Which term is correct for the modern web 2.0 era which we are in? Should I assume to call it a profile picture now over avatar and display picture?