I THINK you need to go into Edit and delete it there but if you send a message to OLI he will take you through it. He got me through the whole joining thing as I got on a muddle as usual and he was great....very patient
Best thing is to email Oli,i know you go to settings and profile image,but it does not tell you how to delete,just try uploading another one,refeshing it,that should work.