I'll be honest: my first reaction to Wayne's photos with baby Nashton on the background was quite... Meh.
I mean, it seemed too horror clichè to me and a little ridicolous.
A creepy and silly little man who tries to be scary.
Then I thought that THAT'S exactly what the Riddler is, in effect.
In comics he feels himself a criminal mastermind and he basically he is very cleaver, but at the same time he is a narcisistic and pathetic man.
So, after the first impression, I change my mind.
BUT...
You need to find a balance between his Jigsaw/John Doe horrorific behaviour and his being a creepy boy.
If you make him too scary he could be ridicolous and annoying.
If you make him too silly you can't take him seriously as a menace.
I think Dano is the perfect actor to find this balance: you just have to see his There Will Be Blood and Prisoners performances to see how he is good to play psycothic and scary man who the audience finds disagreeable and wants the hero to beat the **** out from him.
And that's ok.
The problem would be in the atmosphere and the plot of the movie, especially from the backstory.
I know that we are in a marketing phase where you need to emphasize horror traits of the villain, but I really hope that in the final movie Reeves will be able to find that balance and to have in his hand a plot which has a backstory not too exhagerrated on Wayne's corruption and Nashton's wish of vengeance, but that is sober enough to be emotionally moving.