Cool stuff
This song is unique, and has a lot of neat elements. The background melody you bring in around 1:00 reminds me of slowed down Astral Projection stuff - very cool!
Just a couple of suggestions. First of all, my favorite part of the song, hands down, is the very beginning, with that awesome sweep intro into the song, fading into the eerie piano part. I would have really enjoyed it if there was more of that background pad/sweep effect throughout more of the song. Additionally, the song completely changes tone from 1:15 on, and while I do really like that darker tone there, it gets a bit repetitive by the end and the piano is completely gone at that point. Perhaps some more layers in that section, or possibly keep the piano going? I only say this because by that part I had gotten into a nice feel with the song, and then it completely changed gears.
All things being said, this is a great track with a sweet feel to it, and I will be very interested to hear any changes/additions you make to it, especially if you add vocals like you mention below. Good job!
If you ever get a free moment, please give my song a listen - thanks!