Image
With the Image function, you can replace the default node disc with a custom image.
Common image formats, both bitmap and vector-based, can be imported. The display size is 30 x 30: a larger image is reduced, and a smaller image is centered. The image is saved in the network file.
Usage
Use Node Contextual Menu > Properties > Image > Add to add an image, and Node Contextual Menu > Properties > Image > Remove to remove it.
Propagation
The Propagate Image to the Classes button opens a dialog for selecting the classes associated with the node. All nodes in the selected classes then display the same image, or none if no image is selected.