Yes, you can always change your profile picture at any time.  A blank photo will be put up if you don't have a picture.  Remember a picture will go a long way!  Who wants to chat with a blank profile?.  If you do not want your picture up and your having issue removing it, please create a support ticket to have support help you in removing it. 

To delete your photo tap on the X in the bottom corner of the picture.

A Are you sure? will pop up to confirm the removal of the photo.