So it's most likely either:
- Reptile
- K/Chameleon
- Nightwolf
- A new character
- Story screenshot
- Close-up screenshot of a random background creature just to troll
I don't think it's just a random background creature. The detail is surprisingly good, especially the head. Background creatures are usually very low poly and textured because they are so insignificant and they can't have them being detailed because 1) You won't be able to notice it very well so it's not worth putting a lot of time into it, and 2) putting to much detail into background stuff can cause the game to have performance problems which is a big no-no considering the game needs to stay at a consistent 60fps at 1080p.
While it could be story-related, I think has something to do with a character because the shot looks like it could belong to a character intro animation. It's hard to explain, but the way the camera looks is similar to an intro shot from Injustice 2. Not to mention that it looks like it takes place at Shang Tsung's island and giving the position it could easily be apart of the "battle line" (where the fight actually takes place on a 2D plane).
I don't think it's Nightwolf because he has nothing to do with lizards. K/Chameleon has a chance maybe, but if anything I think they would be a Triborg/TMNT situation where they are a highly customizable character that can basically work as characters that didn't make it in the game -- and released as DLC.
We know that the new characters we are going to see are Kronika and Geras and both their names have something to do with time or old age (which is still kinda time related), so unless one of them are running around with a pet lizard I doubt it's them as it kinda has nothing to do with what their abilities most likely are. It could be another new character which isn't out of the question considering when MKX was first shown they actually showed 4 new characters. However that's because the game had 8 newcomers in total and they still had 4 to show off later. This game may not have as many, so showing 3 right off the bat would be kinda weird. It's hard to say.
Honestly, I think it's just Reptile. He was already leaked by a voice actor and he's one of the original characters so it would be okay for him to be in a reveal line-up (he was in the MK9 E3 build).