Well, justice is a really massive topic to discuss simply because it is one of the core elements of the play. In terms of jurors, you may want to consider the following:
Juror 3 - how he has a skewed view of what punishment is deserved by the defendant due to his own personal bias and experience;
Juror 4 - how his pragmatism interacts with his representation of 1950s Conservativism, and how this relates historically to the McCarthy era HUAC trials.
Juror 10 - how his biased views and prejudices, and his beliefs as to what justice means regarding the case conflict with both the 3rd Juror and the 8th Juror's understanding of justice. Make sure you illustrate a comparison between the 'guilty' verdicts given by both the 3rd and 10th, and the different reasons for it (i.e. racial motivation vs. emotional motivation).
Juror 11 - how his past experiences in a country where justice is innately biased and misused shape his view of the trial, as well as his understanding of justice itself.
There is plenty more to argue with all of the jurors, but this should give you a starting point.