This layout fits personal websites without upper menu.
Assign your favorite theme's number to theme variable. For example, if you want to use theme number 1 (dark-green contrast), write theme=1 in wiki.conf file.
Choosing one of few available themes and headers and footers is always a compromise.
If you are familiar with CSS, you can switch to custom theme by writing theme=custom in wiki.conf file, and edit custom.css file to polish one of freely available design themes or even create your unique design.
Similarly if you know some HTML syntax, set header=custom and/or footer=custom, and edit header.html and/or footer.html
Design theme for a website is like a dress for a human.
Different design themes may affect environments: