Your thumbnails are okay, but they're a little bit cluttered. There's too much going on for me to care about any of it before clicking on it. Your videos are funny, but without editing, not a lot of channels can get big. Good editing is key for channel growth, but if you can have something happening that will keep people invested at all times so they don't click off, than they'll stay on your channel. I think a couple cuts could work for you, but having too many will make it annoying.
TL;DR: Take a little bit out of the thumbnails and cut your videos a tiny bit. You and your group are funny, so you already have a good base for your channel, good luck with your channel man