Umm I know some people that can fake these easily and can freehand life like pictures in a few hours (it's been months since announcement) plenty of time to make renders in Photoshop/Gimp.
I'm not 100% they are real or fake but I know for a fact it can easily be faked in a short period of time(easily one day) and make them look similar to previous revealed character style.
I see what you are saying, but there's much more to this than just an original digital painting.
The characters obviously look 3D, which means either some god-tier Photoshopping is in play or what is more likely; they really are character models. Which means if this is fake, someone had to make a TON of models that look accurate to MK11. The lighting, textures, etc, all look right. The Liu Kang model that we see has the same face as in the trailer, which means they would have to recreate it perfectly or do an insane photoshop on top of the model.
Not to mention the select screen portraits, UI elements, and more that would need to be faked. Not to mention the MK Subreddit and some other MK-related communities aren't allowing people to talk about this and are taking everything down. Ed Boon has also responded to fake leaks in the past with no problem, so considering how big of a deal this one is you would think maybe he would say something.
The amount of work it would take to do this would be more than a few hours for sure. But considering the context of everything that is happening, these have to be real.