Rated 4 out of 5 stars
In answer to the question you asked me, designs should be aligned to the right for the header graphics. And how much of it that you see is dependent on what your screen resolution is. For example, my screen resolution is 1920x1080, so I will only be able to see about 1920 pixels of the right hand side of the 3000 pixels wide image. If you are wanting to see all of the images that you placed on your header graphic, you'll need to move them over to within the width of your screen resolution.
I wrote up a tutorial awhile back that explains a bit more, if you are interested in reading it. It really just has some tips that I may use when creating a design. You can find it here: http://vanillaorchidstutorials.blogspot.com/2015/11/mozilla-themes-focal-point-sizing.html
I hope it helps, and if you need any further help, my email can be found on my profile page.