I have an appendix that contains two full-page figures. The first page of the appendix is always blank except for the title -- I suspect this is a common problem with appendices of full page figures.
I narrowed the problem down to a MWE that, as it turns out can be reproduced without appendices at all. Here it is:
\documentclass{article}
\usepackage[top=1in, bottom=1in, left=0.5in, right=0.5in]{geometry}
\usepackage[demo]{graphicx}
\begin{document}
\section{Big Figure}
\begin{figure}[h]
\caption{Big Figure}
\includegraphics[height=0.76\vsize, width=0.4\hsize]{foo.png}
\end{figure}
\end{document}
which yields

Clearly there is enough room to fit this on a single page.
Changing to height=0.75 yields

Note the excessive white space below the figure.
What is going on here? Why can't this figure be bigger without creating a second page?

{figure}[h!]? Don't both approaches essentially mean "put this box here"? It's not clear to me when you would use one versus the other. – alx9r May 07 '13 at 02:39\begin{figure}[!h]...\end{figure}(which, by the way, is so restrictive that it should be avoided, if possible, and in fact, it's internally changed to[!ht]) still treats the object as a floating object, but overrides values controlling its possible positions; you can see the difference in a real document with some text. – Gonzalo Medina May 07 '13 at 02:58