private Object getThumbnailResource(Node node, String workspace, String generator) {
        Object resource = null;
        try {
            Node imageNode = node.getNode(definition.getOriginalImageNodeName());

The image node is optional for most of custom types. Image provider assumes it always exists and attempts to retrieve the node without even checking for it's existence and as a result using try/catch block to steer execution flow. Furthermore this method does extensive checking for the mime type of underlying node w/o knowing how extending class might treat generation of thumbnails for given resource. This logic should either be removed and safety checks left to getGeneratorImagePath() method or exposed to extending classes for modification.