I have just got a new level of respect for you. Yes everyone who makes banners near the examples you posted are using adamk's graphics pack. I know Adam personally and he is a really nice guy who made the style himself, his pack is available for purchase but that's where it really upsets me. Almost everyone who is using his pack has just got it sent from a friend or whomever. I'm not against using graphics packs, i use some myself.
ex: http://gyazo.com/dd8b7b7be69abd66c55560529bdab8ac
This right here is Alex the smarts pack, when he had his old graphics channel, it provides just flares, colour corrections, and stocks.. That is an actual pack, when you have something like pre-rendered creepers and other stuff its just dumb! For some reason the need to be original has vanished, and if i were a customer i would want to have a origanal banner not just 3D text with a random iron golem standing in the back when your channel has nothing to do with anything anywhere near iron golems? hah.
I stopped graphics but anyone who wants to be a great designer,
BE ORIGINAL