\documentclass{article}
\usepackage{graphicx}
\usepackage{fullpage}

\DeclareGraphicsRule{*}{mps}{*}{} % if you don't recognize the type, it's mps

\newcommand{\umpi}[1]{#1 \includegraphics{unfolding.#1}\vspace{1cm} \\}
\newcommand{\tmpi}[1]{#1 \includegraphics{temp_control.#1}\vspace{1cm} \\}
\newcommand{\smpi}[1]{#1 \includegraphics{stepper.#1}\vspace{1cm} \\}
\newcommand{\dmpi}[1]{#1 \includegraphics{unfolding_data.#1}\vspace{1cm} \\}

\begin{document}
\centering
\smpi{2}
\smpi{1}
\dmpi{2}
\dmpi{1}
\umpi{2}
\umpi{1}
\tmpi{2}
\tmpi{1}
\end{document}
