The message I get the impression from the title that this photo is intended to tell some story, like a hand touching wet paint. But to me it is more of a study in how shadows are affected by the form of the surface on which they appear.
Creative choices The composition is great. Just enough of the stairway is shown to let the viewer know what it is, and other shadows parallel the arm shadow which adds interest. Including the elbow in the arm shadow is effective. The square format works well for this image. The stairway itself isn't really very interesting, and its shape is distorted by the wide angle focal length used here.
Technical aspects Focus is great. Exposure is a bit dark--not dark enough to be a low key photo (an approach that might have worked here to sinister effect), just enough to make me wonder why. Some Levels adjustment would make it look more natural as well as boosting the contrast of the shadow with the background. The shadow of the arm is too blurry, caused I think by a combination of motion blur and a large light source.