\LetLtxMacro{\OldIncludegraphics}{\includegraphics}

\usepackage[export]{adjustbox}
\renewcommand{\includegraphics}[2][]{
  \begin{center}
    \OldIncludegraphics[max width=10cm,max height=6cm,#1]{#2}
  \end{center}}

\renewcommand{\floatpagefraction}{.8}%

\newcommand{\sectionbreak}{\clearpage}