Redefine \partheadmidvskip
to insert the ornament:
\renewcommand\partheadmidvskip{%
\par\nobreak\vspace*{\baselineskip}%
\psvectorian[height=1cm]{102}%
\par\nobreak\vspace*{\baselineskip}%
}

Code:
\documentclass{scrbook}
\usepackage{psvectorian}
\renewcommand\partheadmidvskip{%
\par\nobreak\vspace*{\baselineskip}%
\psvectorian[height=1cm]{102}%
\par\nobreak\vspace*{\baselineskip}%
}
\begin{document}
\part{Part Name}
\psvectorian[height=1cm]{102}
\end{document}
Update: If you want to insert the ornament over (o
) or under (u
) an unnumbered part as mentioned in a comment you can use \setpartpreamble
before this \part*
command:
\setpartpreamble[o]{%
\centering\psvectorian[height=1cm]{102}%
\par\nobreak\vspace*{\baselineskip}%
}
\part*{Unnumbered Part}

Code:
\documentclass{scrbook}
\usepackage{psvectorian}
\renewcommand\partheadmidvskip{%
\par\nobreak\vspace*{\baselineskip}%
\psvectorian[height=1cm]{102}%
\par\nobreak\vspace*{\baselineskip}%
}
\begin{document}
\setpartpreamble[o]{%
\centering\psvectorian[height=1cm]{102}%
\par\nobreak\vspace*{\baselineskip}%
}
\part*{Unnumbered Part}
Text
\part{Numbered Part}
Text
\end{document}