When adding a reference and then an appendix section in LaTeX, compiling it places some (but not all) items from the appendix before references

I want to place two graphs in the appendix of my LaTeX document after the reference section, here's what I did :

\section*{Conclusion}

[...]


\bibliographystyle{plain}
\bibliography{bibliography.bib}

\section*{Appendix}

\begin{figure}
  \includegraphics{Images/Figure1.jpg}
  \caption{Caption}
\end{figure}

\pagebreak

\begin{figure}
  \includegraphics{Images/Figure2.jpg}
  \caption{Caption}
\end{figure}

\end{document}

This doesn't mess up the format but puts every section one after the other, while I'd like to have page breaks between conclusion and references and between references and Appendix. Putting either will make some elements of the Appendix appear before the section.

I used \pagebreak to skip to the next page if that can help.

Thanks for the help !

Your figures do not have any placement specifiers. Using these, you should be able to place the figures as intended, and manage the page breaks independently. Probably using h! or h!t will do the trick:

\begin{figure}[h!]
  \includegraphics{Images/Figure1.jpg}
  \caption{Caption}
\end{figure}

If that doesn't help, you can use [H] of package float to force the figure to exactly that position in the text.