I don’t understand why you want to do that. The :12560 may change over time, since this is a random id Meteor uses, and it might change once you do another build. However, images in the public folder are always available and packaged with the app. Meteor itself cares about pointing the app to the right port (like 12560), all you have to do is use absolute links and omit the public folder: /images/my.image.png This will work just fine.
If you won’t provide a server via --mobile-server, your app will complain on the console that it can’t reach a server backend. But unless you don’t actually need one (since you don’t want to use methods or save something in Mongo), this should just work.
I don’t think it’s possible to run a full-fledged server on the device anyways. The local server on your device is used for starting up the client code and for serving static assets (like those in the /public folder). It also handles Hot Code Push. But if you don’t require a backend, this would be just what you need.