Ranked team rewards design values question

I really enjoyed the idea of ranked teams getting a separate reward class (wards) for end of season as an incentive for team play, as solo queue borders are the only ones that show up for all normal queues (ie a border earned on Twisted Treeline won't show up when you play normals on Summoner's Rift, but a solo queue border earned on Summoner's Rift will show up on Twisted Treeline), suggesting that solo queue is generally preferred.

I was interested in the thought process behind choosing ward skins for the team ranked rewards though. There are two modes you can earn these ward skins in, ranked team 5s and ranked team 3s, and one of those modes doesn't allow wards. Why were ward skins chosen as the team reward and what were the other options considered (and why were they discarded)?