\begin{figure}
\subfigure{\includegraphics[width=67mm]{PipeScannerUnderGround}}
\subfigure{\includegraphics[width=47mm]{CylScanGeometryPipe}}
\caption{}
\end{figure}
produces the following figure:
which seems a little lopsided. I found a nice solution at stackoverflow: Use the \raisebox command to adjust the vertical position of individual subfigures, for example
\begin{figure}
\subfigure{\includegraphics[width=67mm]{PipeScannerUnderGround}}
\subfigure{\raisebox{10mm}{\includegraphics[width=47mm]{CylScanGeometryPipe}}}
\caption{}
\end{figure}
which yields the following result:
Much nicer! :)