Someone else has commented with a list of cities which could be included offline: https://news.ycombinator.com/item?id=34690693

But your workflow is such a hassle that I doubt many people would do it. A more realistic flow (without the list of places above) would be to show an image of the world map, allow the user to zoom in, and let them drop a pin on the map. They can drop a pin near some pixels labeled Paris, but the app doesn't need to know that it's Paris, it just needs to translate the pixel coordinates of the pin (relative to the image) to geographical coordinates, and look for images close to these coordinates.