Another funny thing is that some of the free icons may have been meant to be faction-related. There's a pyramid icon that may have been meant to be a Shurima icon. There's a mountain icon that is almost certainly a Targon icon. The winged sword may be an early Demacian icon. The tree may be an Ionian God-willow. The flower could be a Noxian Black Rose.
But, more recently, with big lore events like the Piltover, Zaun, and Demacia events, we have been getting icons for those factions. Hopefully this trend continues and we'll get icons for all of the places that haven't had lore events yet - Noxus, Ionia, Bandle City, the Void - and then maybe they'll give us icons for the other factions that got events but before they began this trend.