Tikzcd: Filling node with image pattern fails if I apply it on all cells at once

Question

I'm trying to fill some pictures with a background image using path picture as recomended here or here. It works great if I put the style in the cell directly like |[path card]| my content, but it does not compile if I put it inside cells={nodes={path card}}. Any idea what's wrong?

MWE:

\documentclass[]{article}
\usepackage{graphicx}
\usepackage{tikz}
\usetikzlibrary{cd,calc,positioning,shadows}

\begin{document}

\tikzset{
  path card/.style={
    path picture={
      \node[] at (path picture bounding box.center) {
        \includegraphics[height=3cm]{example-image}};}},
}
{
  \begin{tikzcd}[
    nodes in empty cells,
    column sep=1mm,
    row sep=1mm,
    cells={
      nodes={
        inner sep=0pt,
        minimum width=3.9mm,
        minimum height=6mm,
        drop shadow,
        draw,
        fill=white,
        rounded corners=2pt,
        anchor=center,
        shape=rectangle,
        font={\fontsize{4}{12}\selectfont},
        %path card, %% <- uncomment this line, everything breaks.
      }
    },
    ]
     |[path card]| &  & [1mm] & \\
                   &  &       & \\[1mm]
                   &  &       & \\
                   &  &       &
  \end{tikzcd}
}%


\end{document}

Answer 1

You define a style(options) for all nodes, that contain a path picture that contain a node that contain... - problems. Break the infinite recursion with path picture=none (or rather path picture alone to avoid a warning).

\documentclass[tikz]{standalone}
\usepackage{graphicx}
\usetikzlibrary{matrix,shadows}

\tikzset{
  path card/.style={
    path picture={
      \node[path picture] at (path picture bounding box.center) {
        \includegraphics[height=3cm]{example-image}};}},
}

\begin{document}
\begin{tikzpicture}
\matrix [
matrix of  nodes,
nodes in empty cells,
  column sep=1mm,
    row sep=1mm,
      nodes={
        inner sep=0pt,
        minimum width=3.9mm,
        minimum height=6mm,
        drop shadow,
        draw,
        fill=white,
        rounded corners=2pt,
        anchor=center,
        shape=rectangle,
        font={\fontsize{4}{12}\selectfont},
        path card,
    },
]{
 & &[1mm]  &\\
 & & &\\[1mm]
 & & &\\
 & & &\\
};
\end{tikzpicture}
\end{document}