They go in public/packages/[vendor]/[package]/
, so you can refer to them as <img src="{{ asset('packages/vendor/package/image.png') }}">
.
As for not having to republish, Laravel doesn't provide such a way, but yes you could, in development, set up a symlink between the directories, or set up a filesystem watching process (like Grunt can do) to automatically publish assets if you change something.