\documentclass{article}
\usepackage{pstricks}
\usepackage{pst-slpe}
\pagestyle{empty}
\parindent=0pt

\begin{document}

\begin{pspicture}(12,5)
\psset{fillstyle=slopes}
\pscustom{\psccurve(0,0)(3,5)(5,3)(7,5)(8,2)(12,5)(11,2)(9,0)(7,1)(3,2)}
\end{pspicture}

\end{document}

