Hi ! I got a simple idea today. Add pictures on signs with Spout. Yeah, I know it's not really possible, my idea is to "link" an image to a sign, when an user click on the sign, the image appear in a pop-pup There would be a simple command: /signpic <link> Hope someone is interested.
You should go and ask the SpoutDev team about this I don't think this is implemented yet, nice idea though
Maybe one can abuse the entity skin functions to implement painting skinning? Never mind, the client is coded to ignore skinning packets for any entity ids that are not EntityLiving.