While I was setting up my YouTube channel, I wanted to create some sort of graphic for the channel art.
YouTube provides a great explanation of the sizes for different devices but I found myself recreating the guides in Photoshop when I was working on my channel art graphic.
I ended up with a pretty hastily made template that mimics the provided template graphic, except it is a Photoshop CS5 file with layers, just like an onion.
Just in case this could be helpful, here are the downloads for the full size PNG guides and the Photoshop file I ended up with.
If you found this of use please let me know below in the comments!