Sstrhsrtj

I found the following picture of snowflakes:

begin{tikzpicture}[decoration=Koch snowflake]

    draw decorate{decorate{decorate{decorate{(0,0) -- (3,0)}}}};

    draw decorate{decorate{decorate{decorate{(3,0) -- (1.5,-3)}}}};

    draw decorate{decorate{decorate{decorate{(1.5,-3) -- (0,0)}}}};

end{tikzpicture}

Can I use it to replace circles (nodes) of a graph drawn in tikz? This is my graph:

begin{tikzpicture}

  [scale=.6,auto=right,every node/.style={circle,fill=yellow!70}]

  node (n6) at (31,20) {6};

  node (n4) at (34,18)  {4};

  node (n5) at (38,19)  {5};

  node (n1) at (41,18) {1};

  node (n2) at (39,16)  {2};

  node (n3) at (35,15)  {3};



  foreach from/to in {n6/n4,n4/n5,n5/n1,n1/n2,n2/n5,n2/n3,n3/n4}

    draw (from) -- (to);



end{tikzpicture}

According to what I find, the perhaps most straightforward way of achieving this is to employ pics.

documentclass[tikz,border=3.14mm]{standalone}

usetikzlibrary{decorations.fractals} 

tikzset{pics/.cd,

snowflake/.style n args={2}{code={%

begin{scope}[decoration=Koch snowflake]

    draw[#1] decorate{decorate{decorate{decorate{(-1.5,1) -- (1.5,1)}}}};

    draw[#1] decorate{decorate{decorate{decorate{(1.5,1) -- (0,-2)}}}};

    draw[#1] decorate{decorate{decorate{decorate{(0,-2) -- (-1.5,1)}}}};

    path[#1] (-1.5,1) -- (1.5,1) -- (0,-2);

    node at (0,0) {#2};

    end{scope}}}}

begin{document}

begin{tikzpicture}[scale=.6,auto=right]

  pic[local bounding box=n6,scale=0.3] at (31,20) {snowflake={fill=yellow}{6}};

  pic[local bounding box=n4,scale=0.3] at (34,18)  {snowflake={fill=yellow}{4}};

  pic[local bounding box=n5,scale=0.3] at (38,19)  {snowflake={fill=yellow}{5}};

  pic[local bounding box=n1,scale=0.3] at (41,18) {snowflake={fill=yellow}{1}};

  pic[local bounding box=n2,scale=0.3] at (39,16)  {snowflake={fill=yellow}{2}};

  pic[local bounding box=n3,scale=0.3] at (35,15)  {snowflake={fill=yellow}{3}};



  foreach from/to in {n6/n4,n4/n5,n5/n1,n1/n2,n2/n5,n2/n3,n3/n4}

    draw (from) -- (to);



end{tikzpicture}   

end{document}

The cleanest way would probably be to define a new shape. Given the complexity of the shape, this might not be straightforward, but it is conceivable that it is not impossible. Another option would be to use a path picture of a node, but like in the pics above that would "only" lead to background pictures and in particular not define the boundary of the nodes, meaning that the gaps in the lines connecting the snow flakes would be similar to above. (They may become slightly smaller if you base the node on a circle shape, but path pictures have other subtleties which is why I removed this part of my earlier answer.)

Note that, if you are concerned about the gaps in the lines connecting the nodes, there is a simple fix.

documentclass[tikz,border=3.14mm]{standalone}

usetikzlibrary{decorations.fractals,backgrounds} 

tikzset{pics/.cd,

snowflake/.style n args={2}{code={%

begin{scope}[decoration=Koch snowflake]

    draw[#1] decorate{decorate{decorate{decorate{(-1.5,1) -- (1.5,1)}}}};

    draw[#1] decorate{decorate{decorate{decorate{(1.5,1) -- (0,-2)}}}};

    draw[#1] decorate{decorate{decorate{decorate{(0,-2) -- (-1.5,1)}}}};

    path[#1] (-1.5,1) -- (1.5,1) -- (0,-2);

    node at (0,0) {#2};

    end{scope}}}}

begin{document}

begin{tikzpicture}[scale=.6,auto=right]

  pic[local bounding box=n6,scale=0.3] at (31,20) {snowflake={fill=yellow}{6}};

  pic[local bounding box=n4,scale=0.3] at (34,18)  {snowflake={fill=yellow}{4}};

  pic[local bounding box=n5,scale=0.3] at (38,19)  {snowflake={fill=yellow}{5}};

  pic[local bounding box=n1,scale=0.3] at (41,18) {snowflake={fill=yellow}{1}};

  pic[local bounding box=n2,scale=0.3] at (39,16)  {snowflake={fill=yellow}{2}};

  pic[local bounding box=n3,scale=0.3] at (35,15)  {snowflake={fill=yellow}{3}};

  begin{scope}[on background layer]

  foreach from/to in {n6/n4,n4/n5,n5/n1,n1/n2,n2/n5,n2/n3,n3/n4}

    draw (from.center) -- (to.center);

  end{scope}

end{tikzpicture}   

end{document}

I am, of course, not claiming that the lines hit the "nodes" precisely in the same way as pgfpointshapeborder would, but since these snow flakes are sort of spherical, it almost works.