Have the image show up only for a certain visibility/reveal %. Thus, in a hexcrawl. The players will see the image (world map) but once they learn about a location (not visited/explored), the gm can grey it out (just like you would make it 70-80% reveal). The image wouldn't show up on that. I don't know feasible or performance-wise it would be. If it's too much of a hassle, then no problem.
Have the image show up only for a certain visibility/reveal %. Thus, in a hexcrawl. The players will see the image (world map) but once they learn about a location (not visited/explored), the gm can grey it out (just like you would make it 70-80% reveal). The image wouldn't show up on that. I don't know feasible or performance-wise it would be. If it's too much of a hassle, then no problem.