Hey there,
Lovely song, fantastic vocals. You obviously haven't overthought your chord progressions too much, as they all fit and sit just right, you clearly know what you're doing. I was expecting it to sound a lot less "finished". I don't think you'd need to do much more arrangement wise, I'd steer away from drums. Do you know Bon Iver or Fleet Foxes? In my head I can hear it as one of their more understated songs, though with more of Robin's (Fleet Foxes) vocal style than Justin's (Bon Iver). Perhaps look into using a guitar amp, whether a real one or virtual modelling software, to pass a guitar through a series of delay/resonance pedals. Reverse the delay, set the mix to about 85-90%, and up the resonance, and you'll get yourself an ambient yet structured layer that your defined parts can sit on top of. It won't change the feel too much, it'll still sound organic, but it'll fill it out a bit. I would also maybe slow it down a bit, and start off a bit softer and build it, build it, build it, hit it and then go right back down at the end, but that's just a personal preference thing and the song is still awesome with or without!
