Header on background only…catch box theme

would like my header to be on my background and not use the appearance header at all. The problem I have is when I do this it makes the post page/menu bar etc. go to the top of the website and covers up the background.

Is there a way to make it start where it normally would with the appearance header?

I tried making a dummy transparent header and load it in the appearance header but it just shows white..even with a png..

Would love and appreciate some ideas..