How to add a picture over header, on right side?

Thank you for this great theme! I like it. I would like to know 2 things:

How to add a picture on the right side of the header that is on top of the standard green header background. I know I can add a logo but it is programmed to show up on the left side of the header.

How can I change the header banner altogether so it's more like a banner graphic? I don't know much about coding but I do know enough to see that the header is actually made up of a thin "slice" picture that just repeats all the way across.

Thank you!