Tags seem to indicate that this is the uniform from Lucky Star (never seen that or Hetalia), not sure how to tag that since it's not cosplay of a character.

Just cosplay and lucky_star. It doesn't have to be a particular character.

I can't help but think it's Konata - the eyes and mouth are just right, and isn't she the main character in the opening doing that gesture?

Looks more like Misao.