Graphics around page number

Here a solution which modify \pagemark command and use \vrule to draw rules beside page number, you can modify thickness of rule by adding width<dim> to vrule like this:

\vrule width1.5pt height1.5ex depth2.5ex 

To change color of rules

{\color{your_color}\vrule width1.5pt height1.5ex depth2.5ex}

In this case you need to add xcolor package

---

\documentclass{scrbook}
\usepackage{xcolor}
\usepackage{lipsum}
\renewcommand{\pagemark}{{\color{gray}\vrule width1pt  height1.5ex depth2.5ex \ 
{\color{black}\arabic{page}}\ \vrule  width1pt height4ex depth0ex }}
\begin{document}

\lipsum 

\end{document}