Firstly, one picture won't prove much. Fakers put a lot of effort into making a single picture, but their descriptions of the craft often entail it performing some fairly complex manouvers over a period of some time. The photgraphic record is never consistent with the reported activity.
So, in your hypothetical scenario, I'd expect photographs of the craft flying, landing, aliens disembarking, and setting up that bbq. All from consistent viewpoints, with the White House, or other landmark clearly visible in the background. Another witness caught in some of the photographs, who can be contacted, recognised, and who also has pictures with the viewpoint, with a corroberating story, would be nice.
But this is not what we get. We get single, blurry images, in tight zoom, without any points of reference, for scale, or location.
btw Skinwalker;
http://www.iwasabducted.com/ufogallery/ufo107.jpg
my friend's mum had that lampshade, so I think it's a reflection in a house window, looking back into the room, ....!