Here's some game mode ideas for rotating queue.

With rotating queue being a thing now. We can have a whole bunch of new game type ideas. Here a few of mine but I'd love to hear other suggestions

Season Flashback Whether it's nostalgia or out of curiosity, most of the fresh blood would love to play league in its "glory days." Make it a standard game on summoner's rift but with only the content available at the end of an early season like season 2 or 3. Bring back the old baron, the old map, etc. as someone who joined in season 5 it would be interesting to see how the game played back then.

Toxic Treeline An otherwise standard game of 3v3 on twisted treeline with 3 catches. All champs have a 15% spell vamp, all sources of health regen (except for mundo's ult) is inversed, and the neutral objectives cure this status for 5 minutes.