Absolute positioning in beamer

Here it is a simple solution taken from Section 17.13.2 of Tikz & PGF manual (section subtitle: "Referencing the Current Page Node – Absolute Positioning").

For example, to put a figure in the top right corner, you can use:

\begin{tikzpicture}[remember picture,overlay]
    \node[xshift=-2cm,yshift=-2cm] at (current page.north east){%
    \includegraphics[width=2cm]{photo.png}};
\end{tikzpicture}

The key in the code above is the combination of current page.north east (which fixes the reference point), and the xshift and yshift variables (which shift the image from that reference point).

Naturally, you can use any other reference point like current page.center, current page.south west, etc. Then, just achieve desire absolute placement using xshift and yshift.

The list of reference points for current page.blah include eight major cardinal directions (north, west, south, east and the four in between), plus center. It is also possible to use any degrees (0-360), where 0 is east and 90 is north (for example, current page.45 for the top right corner).

The textpos package has been designed for absolute positioning of text and graphics on the page.