Hmm...
Windy day, open window, a picture in a frame standing in it...
...is the glass in the picture cracked? Or is it a person? Hmm...
23 marks on the wall under it... a rack wiiith a flute?
I'm not sure about the card-thing down and to the left.
Based on the title, and what I think when I see this, I think the story behind this is:
The person the things belong to are missing the person in the picture, they have marked on the wall how many days it has been since they last saw each other, and to reduce the pain of missing them, the person opened the window, and played the flute, thinking fondly of their dear friend.