This is pretty solid! The piano and harp play nicely with each other and the chord progression is nice and somber, perfect for the isolated vibes in the painting. The vibes are great and it creates a strong setting. I do agree with EinelTheFox here in that the next thing I would personally look at would be giving it some more movement and telling more of a story, whether that be through adding instruments, a more drastic change in chord progression, or whatever else. This doesn't take away at all from what's there though, because it's very good! 

For a first timer this is solid! Chordal choice was quite interesting at times and the melody was well structured with breathing pauses and good variation with a calm gentle nature.
However I feel like there could be more. The song itselfe is good but it feels like its stuck a bit and needs some variation. Maybe having the melody played by different instruments, introducing a counter melody like an ask and response thing with the melodys or playing with the dynamic of the song to let the song tell a story and take the listener to where you want him to be.

Needless to say, this is complaining at a high level and those are points I would criticise with composers with much more experience. So please just see those points as a friendly suggestion. :) Because you did quite well.