I made it all the way to Gold League before the end of the Season, so I received 22 Loot Chests to open yesterday. Ended up getting some pretty nice reward cards (1 Epic and a few Rare ones) for my collection -
I've been bumped back down to the Silver Leagues now, but I don't think it will take me too long to reach Gold again since I've finished opening all my booster packs now (finally) and have leveled up my cards. I zoomed through the daily quest today pretty quickly and only had to fight 8 battles to complete it. I received 2 more Reward cards for my troubles, both of them Rare -