Header Image

The blogger.com, i.e., blogspot.com simple template which we have been using has an option to add a background image and to have that image adjust its size to fit.

The result is not acceptable except for the mobile view.

But this one minor edit to the template HTML for the default CSS style gives a good result:

#header img {
width: 100%;
max-width:100%;
margin-$startSide: auto;
margin-$endSide: auto;
}

Select "Proceed" when warned about doing edits to the HTML. Be sure to preview the result before saving the template.