Background images not working

[alinex]

Within the example from http://blockdiag.com/en/blockdiag/examples.html works but not the background images.

<!-- prettier-ignore -->
blockdiag {
   // Set boder-style, backgroun-color and text-color to nodes.
   A [style = dotted];
   B [style = dashed];
   C [color = pink, style = "3,3,3,3,15,3"]; //dashed_array format style
   D [color = "#888888", textcolor="#FFFFFF"];
   // Set border-style and color to edges.
   A -> B [style = dotted];
   B -> C [style = dashed];
   C -> D [color = "red", style = "3,3,3,3,15,3"]; //dashed_array format style
   // Set numbered-badge to nodes.
   E [numbered = 99];
   // Set background image to nodes (and erase label).
   F [label = "", background = "_static/python-logo.gif"];
   G [label = "", background = "http://blockdiag.com/en/_static/python-logo.gif"];
   H [icon = "_static/help-browser.png"];
   I [icon = "http://blockdiag.com/en/_static/internet-mail.png"];
   // Set arrow direction to edges.
   E -> F [dir = none];
   F -> G [dir = forward];
   G -> H [dir = back];
   H -> I [dir = both];
   // Set width and height to nodes.
   K [width = 192]; // default value is 128
   L [height = 64]; // default value is 40
   // Use thick line
   J -> K [thick]
   K -> L;
}

The output is:

But it should look like:

How can I also get background images included?