Beamer: How to place graphics at the bottom of a frame

Beamer: How to place graphics at the bottom of a frame

I want to achieve that included graphics are always on the bottom of the
frame, so that their position isn't influenced by the length of the text
above.
I tried the figure enviroment without success and the \vfill also doesn't
give the wished success.
Here is some similar example source:
\frame{
\only<1-3>{Blablabla1}
\only<4>{Blablabla2}
\only<5>{Blablabla3}
\only<6>{Blablabla4}
\only<7>{Blablabla5}
\only<8>{Blablabla6}
\only<9>{Blablabla7}
\vfill
\visible<3->{%
\includegraphics<1-3>[width=\linewidth]{img/1.png}
\includegraphics<4>[width=\linewidth]{img/2.png}
\includegraphics<5>[width=\linewidth]{img/3.png}
\includegraphics<6>[width=\linewidth]{img/4.png}
\includegraphics<7>[width=\linewidth]{img/5.png}
\includegraphics<8>[width=\linewidth]{img/6.png}
\includegraphics<9>[width=\linewidth]{img/7.png}
\includegraphics<10>[width=\linewidth]{img/8.png}
}
}