[2019] Here's how you can change the main menu, if you don't like the current winter themed one (only on PC)

Go to

...\Steam\steamapps\common\rocketleague\TAGame\CookedPCConsole

find the files BG_Stadium.upk and BG_UtopiaSnow.upk and rename them vice versa.

You can do this also with BG_Beach.upk in the summer. Or whenever Psyonix decides to change the main menu (like with the upside down fall main menu).

Bonus points: You can even change your main menu to the new chinese map. It's called BG_CHN_Stadium.upk

@Psyonix

How about you guys just give us the option to disable these themed main menus?