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.