No expert advise here just my 2 cents. Ann I do not think there is a way to really tell if an image is of a ghost, I think it would depend on what you believe it to be because you took the photo and are the only one to really know all of the circumstances and details when you snapped the photo. This looks like a ghost to me, and it is a very cool picture.
I saw a ghost once of a guy that I knew right after he passed away, and you could not tell he was a ghost, he looked like a real person wearing real cloths just like he always did, he also sat down at the table and said good by to my friend which was his best friend. The only way I could tell he was a ghost is I watched him walk away and when he got about a half block away he just faded away.
If you think its a ghost then that is what it is.