This is a short LaTeX package which greats a random grid of shapes. At the moment, the shapes are harded coded to be red triangles, black squares, and a red square. The package file can be downloaded here. A simple example is:

 \documentclass{article}
\usepackage{tikz}
\usepackage{randomgrid}

\begin{document}
\begin{tikzpicture}
 \matrix[matrix of shapes,row sep=1cm,column sep=1cm,odd one out] {\\};
 \end{tikzpicture}
 \end{document}

This produces the following:

A more detailed explanation of the ideas behind this package can be found on the TeX-SX blog.