New to youtube need help with a few things

Hey so I just created a youtube channel: you can find me if you search Taylor Scott th 10 farming or something like that. Anyways I've recently taken the interest into uploading videos on how I raid and so on about clash of clans. I think it would be cool if I had a custom thumbnail, channel art, and an intro to my videos.(channel art has to be like 2560x1440 and so its hard to find pics that fit that). However, I don't know how to make cool stuff like that…if anyone could help me, or create something for me it would be much appreciated. My clash name is Pokmaster which I hope can be incorporated into the channel art or custom thumbnail with some witches or something similar to that would be cool.

Any help is appreciated !