Peter reminds his fellow-elders that if they serve Christ well they will receive from him ‘the unfading crown of glory’. This is obviously a form of reward, but it will not be a reward given by an appreciative church (that can happen in this world and it is a good thing to do for all faithful elders); instead it will be given by a pleased Master.
What will the reward include? One aspect will be for an elder to see in glory those he helped when he was an elder. He may not have realised the way that the Lord was blessing such involvement, but he will see that the Lord did use him. He will discover that the hours he thought were fruitless, the many prayers he offered and thought were not heard, were actually the opposite and he now sees those individuals reflecting the glory of Jesus.
Another aspect is that the enjoyment of the reward never diminishes. The reward will be an eternal reminder that Jesus, who never forgets, is always pleased with what his dedicated elders did for his flock that he left in their care during their time on earth.
The other aspects? We can wait until we get there to find out! Meanwhile we have a call as a congregation to pray for our elders and submit to them, and for our elders to continue to tend the flock of God.