I'm actually not familiar with the character but i do agree with Patcave. Get the eyes to reflect more. Especially if the eyes are other than black.
Also, I like the compositions and the posing are good... but maybe make it more...spontaneous. Or if anything exaggerate the posing more. I'd like you to really hang onto that rail in the first picture. Really tilt that head in the second picture. And actually look like you're going to take out a book in the last picture.
It might be just me, but I like documentary pictures... But all in all, I think that will really impact the pictures more.