Hmm, aside from the crossword and the achievement pic, the only other hint I could think of was that one tweet from Boon (though it could just be Boon's typical joking behavior)
https://twitter.com/noobde/statuses/307925240489574400
RT FrogLantern @noobde I have been eagerly anticipating Captain Cold. These Killer Frost rumors make me sad. 
EB: Stay Frosty! #Hicks
From the original debut trailer for Injustice, we know there is at least one character who uses ice beams (the one shooting Flash). If the roster for Injustice really is only 24 characters, and if 3 out of the final 4 character slots are really gonna be Black Adam, Ares, and Raven, then that 4th and final slot (who would be the mystery woman from the achievement picture) just has to be the ice user.
However it's entirely possible that the roster is greater than 24 characters, and maybe Captain Cold was the ice character shooting at Flash, and maybe the the mystery female in the center of the achievement pic is some pale redesigned version of hooded Circe. We'll see.
I'm just gonna throw this out there...since nobody else has...
Just because there was ice going towards Flash in the announcement trailer, doesn't guarantee that there will be an ice powered character included. For all we know, it could have just been done for effect. Because it looked cool.
Nothing really concretely says it has to be a confirmed playable character. Could be in reference to Captain Cold, but he's not actually playable, just in story, or not in at all.
One thing I will point out to add to this potentially being the case, is that the character shooting the icicle, isn't shown in the slightest. Even Lex, who wasn't revealed 'til way later, was shown enough to make it obvious it was him.
Not saying this is the case, but people act as if it's a guarantee that there's an ice powered character in the game based on that first trailer.
This seems like the most likely scenario to me, and the roster is definitely more than 24 going by what Hector said at NYCC.
Even though some of the evidence has been pointed at more than 24 characters, and I believed it to be the case, it probably makes the most sense at this point that it's likely to be 24. Hector did say the select screen was a decoy, but that doesn't mean the real select screen has more spots. He also said they weren't even halfway there in terms of revealing the characters, but people make the misconception that he was counting 12 when he said that. If you look at the interview, he says "we're about 12 characters in and we aren't even halfway there". Key word being
about. Which
can mean 12 isn't halfway, but could also mean about 12 isn't halfway(such as 10 or 11 being about 12).
Not saying it can;t be more, but I don't think his word choice neccissarily was clear enough to confirm there's more than 24 for sure. I hope so though.
