I think some basic combat statistics would be rather nice
I am thinking along the lines of the total war series
First: A small description of both opponents armies before going in, maybe just the amount of infantry,cav, archers they have etc. plus interesting unique such as mages or dragons etc. This would be nice as you would now know if you are attacking an army or a helpless baggage train. Possibly if you are worried about players screening this for easy looking armies to kill, only give it to defenders?
Secondly: A battle recap, it would be nice to see which units you and your opponent lost/killed, plus who's leveled up and then finally maybe a list of what plunder you gained from the fight.
I think this would be a nice little touch and hopefully not something too difficult?