This is very subtle, elegant and soothing. I love that it is monochromatic. I wonder what it would look like if it was a little lighter, even though I love it just the way it is.
I really like the formal arrangement, but the center of interest in this photo is the vertical vase of flowers and the way it's cropped it does not demonstrate the rule of thirds.
I like the linear quality of this. The vase needs to be more to the right to truly be within the rule of thirds grid. I'd straighten up the shot so that the lines of the shadow and light are perfectly perpendicular to the bottom line of the shot. They appear to be slightly off to the right. I like the lighting and the clarity of the glass vase's shine.