There are two issues, it would appear from the OP's comments: 1) insetting an image, and 2) eliminating/masking the transparancy of the inset. I will address the issues in turn:
IMAGE INSET
Here I give two examples using \stackinset
. The first flush to the bottom right corner, and the second with some border. I use \includegraphics
for the images, but tikz
code or similar things can go in their place.
\documentclass{article}
\usepackage{stackengine,graphicx}
\begin{document}
\noindent\stackinset{r}{}{b}{}{\includegraphics[width=2in]{example-image-A}}
{\includegraphics[width=\textwidth]{example-image-B}}\medskip
\noindent\stackinset{r}{15pt}{b}{25pt}{\includegraphics[width=2in]{example-image-A}}
{\includegraphics[width=\textwidth]{example-image-B}}
\end{document}

Here's a version with a white border:
\documentclass{article}
\usepackage{stackengine,graphicx,xcolor}
\begin{document}
\fboxrule=5pt\relax
\fboxsep=0pt\relax
\noindent\stackinset{r}{}{b}{}
{\color{white}\fbox{\includegraphics[width=2in]{example-image-A}}}
{\includegraphics[width=\textwidth]{example-image-B}}\medskip
\end{document}

MASKING INSET TRANSPARANCY
To deal with a transparent inset image-A, place it on a white \colorbox
:
\documentclass{article}
\usepackage{stackengine,graphicx,xcolor}
\begin{document}
\fboxrule=5pt\relax
\fboxsep=0pt\relax
\noindent\stackinset{r}{}{b}{}
{\colorbox{white}{\includegraphics[width=2in]{example-image-A}}}
{\includegraphics[width=\textwidth]{example-image-B}}\medskip
\end{document}