Thread:Semantic-mediawiki.org:Community portal/Images in Graphviz nodes - which path to use?

I need to create a graph with the Graphviz extension, in which the node is filled with an image. "Image" is used as an attribute in a "node" definition. An example is found here: http://www.graphviz.org/content/kennedyanc. However, that example does not run on MediaWiki, which has a different way to store images. That could be a problem. According to the extension description at https://www.mediawiki.org/wiki/Extension:GraphViz, a restriction states that "Any image attribute values are required to be the names of uploaded files". Okay... but whatever I do, just the filename, or the full link to the file in the images folder, it doesn't work. The system error message is "The dot image attribute must be the name of an uploaded file". Has anyone worked with this and found a solution?