You can load package scrlayer-scrpage
which is part of the KOMA-Script bundle. Then you can declare a new layer for the image and add this layer to every pagestyle (including empty
):
\usepackage{scrlayer-scrpage}
\DeclareNewLayer[
background,
align=bl,
hoffset=1.5in,
voffset=\paperheight,
addvoffset=-.3in,% <- adjust this value to your needs
mode=picture,
contents=\putLL{\includegraphics[width=2cm]{example-image}}
]{letterimage}
\AddLayersToPageStyle{@everystyle@}{letterimage}
Example:
\documentclass{scrlttr2}
\setkomavar{fromname}{Name}
\setkomavar{fromaddress}{Address}
\usepackage{lipsum}% <- only for dummy text
\usepackage{graphicx}
\usepackage{scrlayer-scrpage}
\DeclareNewLayer[
background,
align=bl,
hoffset=1.5in,
voffset=\paperheight,
addvoffset=-.3in,% <- adjust this value to your needs
mode=picture,
contents=\putLL{\includegraphics[width=2cm]{example-image}}
]{letterimage}
\AddLayersToPageStyle{@everystyle@}{letterimage}
\begin{document}
\begin{letter}{Recipient\\Address}
\opening{Hallo,}
\lipsum[1-10]
\closing{Best regards}
\end{letter}
\end{document}

\AddToShipoutPictureBG{% \AtPageLowerLeft{ \raisebox{1cm}{\hspace*{1.5in}\includegraphics{Logo_unten.eps}} } }