A Marine does not lie, cheat, or steal. A Marine would never post a picture of a deceased comrade in arms and lie and say it was his. A Marine would never cheat and pass off a photo on a website of a person who is dead and can't defend himself. And, a Marine would never steal a photo that belonged to someone else and post that photo telling that this photo was his.
Finally, you don't know the Gifford family. You only mentioned the name, "Gifford," because I found out the identity of the deceased Marine whose photo you posted and you were caught and are now facing the humiliation.
Who is going to believe you were ever a Marine after pulling such a disgraceful and shameful act today?
What you did was not a mistake and you knew from the very beginning that your action was wrong.