\usepackage[firstpage]{draftwatermark}
\SetWatermarkText{
 \hspace*{4.5in}
 \raisebox{9.5in}{
  \includegraphics[height=0.9in]{artifacts_available.pdf}
  \includegraphics[height=0.9in]{artifacts_evaluated_reusable.pdf}
 }
}
\SetWatermarkAngle{0}