Bored when playing pokemon.. what next?

I have diamond for ds and i beat the elite four multiple times, caught heatron and uxie and azelf.. i am currently attempting to complete my national dex thing but it is really hard (is the only way to complete that by seeing pokemon useing the radar? and trading or whaat). anyways yea i dont know what else to do on the game, any thing i missed? oh and what happened to team galactic i dont remember defeating them but i beat the elite four soo i dont know.. ideass??