I don't think you are totally safe but you don't need to worry too much either. First of all, can that guy prove that the picture was taken the same day accident happened? Holding a bottle of beer does not mean you were drunk. Second, if he knew that you were driving under influence why did not he call the police then? Above all, he came up DUI theory after the insurance company denied the claim.

So, talk to a lawyer and next time this guy calls you ask him to talk with your lawyer. Your insurance company might help you with a lawyer. Talk to the insurance company first. No need to go into details of how many bottles in how many hours and how much body fat. That's the lawyer's job :)