# Adjust the location and size of beamer's framebox for a custom theme

I am trying to create a simple custom beamer theme for presentations by my lab at school.

Our department has a relatively nice powerpoint theme as shown below which I have for the most part successfully replicated in beamer using

%\newlength{\myheight}

\setbeamertemplate{background}{
\begin{tikzpicture}
\useasboundingbox (0,0) rectangle (\the\paperwidth, \the\paperheight);
\node[inner sep=0pt,anchor = north west] (header) at (0,\the\paperheight)
{\includegraphics[width=\the\paperwidth,trim=0.01in 9.05in 3.15in 0.45in, clip]{WVU-Pattern-Thin-295-Coated}};
\node[inner sep=2pt,anchor = north west] (wvlogo) at ($(0.025*\the\paperwidth,0.97*\the\paperheight)$)
{\includegraphics[width=0.3\paperwidth]{Engineering-FL-124andWhite}};
\node[inner sep=0pt,anchor = west] (website) at ($(0.765*\the\paperwidth,0.888*\the\paperheight)$)
{\hypersetup{colorlinks=false} \fontseries{m} \fontfamily{phv} \tiny \selectfont \color{white} \href{http://www.statler.wvu.edu}{www.statler.wvu.edu}};
%\global\settoheight\myheight{\includegraphics[width=\the\paperwidth,trim=0.01in 9.05in 3.15in 0.45in, clip]{WVU-Pattern-Thin-295-Coated}}
\end{tikzpicture}
}


where the images represent the background and logos.

Now everything is working decently well (at least for me and my labmates to use) but I would like to tell beamer to shrink the frame boxes to only include the area beneath that header that will show up on every frame (except for plain frames which I still need to implement)(i.e. I want the text/titles/footers/etc to show up in the white space).

Is there some way to do this? I've tried messing with shrinking \textheight as can be seen in the commented portions of my code but the framebox just shrinks in this case and still starts at the top. I need some way to shrink it and offset from the top and I haven't been able to figure out how to do this by looking at the beamer class file. As I write this I am thinking maybe the issue is that I should define this as a header rather than a background although I'm not entirely sure how to deal with the tikzpicture in this case.

You can find my code with a minimum example posted here which can be compiled using pdflatex.