You had me questioning myself until this line. Are you familiar with the internet?

Some people literally just get their jollies off misleading people. My automatic stance to unverified information on the internet has been 'extreme superstition' ever since the rumour went round that you could charge an iphone with a microwave
TBF, i hadn't considered the fact that they were photographs, so credit to you, they look more legit that i thought.
Yes, but my question was this; why if they had fabricated these for a joke, would they not yet have revealed it was fake? And yes, there are people who screw around and enjoy upsetting others on the Internet, but here? These forums are clearly not a place for the sort of people who do stuff like that, they can stick to the Civ page on Reddit (have you seen the stuff they post there? I'd quote some, but perhaps that wouldn't be such a good idea).
Well, don't ignore valid arguements because I make some that you deem silly; even people you would consider not especially intelligent can sometimes have interesting and useful insights.
But your scepticism is healthy, and I too can see problems. It is true that these pictures being photos of a screen does merely add an extra small step to faking these. And the fact that the person that posted these has not even defended himself, just gone completely silent, is suspicious, especially as it contradicts his claim to being a frequent user (which if true would suggest he had some sort of respect for the community, and so would not pull off something like this). Though he only recently joined, he claims to have been lurking on here for years; that is not impossible, as I too have been reading things on threads on this site every now and then since around 2010 without an account, but the fact that he has then not posted much since he has joined besides these leaks might suggest he is not a frequent user, and he joined having recently discovered these forums for one reason only; to troll people. This would explain why he had not revealed he was joking; he came here, had his fun, and now he's gone.
Then again, he claims the pictures are from 'a friend', and he is no more in the know than the rest of us, and this could be true (even then though, his friend could have faked these without him knowing). However, he then seems to contradict this by saying he has reason to know the pictures are not faked. Also, him saying something along the lines of 'Looks like the Ottomans are in, not a surprise, they are in every game' seemed a little like he was deliberately mirroring arguements that have been made on this thread, so as to make people more likely to believe it. He also claims the Ottoman leak will likely be the last; why he be sure of this- this could interpreted as sound like part of a plan.
Also, I can see it being argued that Firaxis would not have made these video thumbnails weeks in advance.
Still, all this being said, I, though unsure myself, have not yet completely written off these leaks yet. I suppose the only way we will know the truth will be if Sumer or Roman leaders have backgrounds like that in their reveals, or if the Ottomans are/aren't revealed. And, at least for the background for Trajan of Rome, that looks to be the case.
I voted Germany, because it fits in with being Gamescon this week!
If I knew about that when I voted, I would have too.