You did a good job pulling the text out of the manga cover, and I absolutely adore the image, but you may run into the problem of the wallpaper being considered a "scan to wall." Basically meaning that its only a spruced up version of the scan with no original backgrounds or various other things to it. I personally think that the wall is fine and should be ok for the galleries, I just bring this to your attention so you are aware that it is possible the wall will be rejected. I certainly hope not though, I think this wall would be a great addition to the sparse Mushi-shi gallery we have here.

And as for the crediting, if someone else does the scan or vector, you credit them, and credit yourself for the design/creation. In this case, you would credit yourself as the scan/designer. Not that its a bad thing to credit the original artist, I think thats nice and polite, but its not necessary.

I hope to see this in the galleries soon!

-Cheers