Cool piece here and I think what you need is some contrast to give this depth and drama. You can really accentuate the the flashlight’s lighting and use it to create that depth and drama as well as giving this piece a nice focal point. Think about a flashlight at night, it highly illuminates what it is hitting and cast drastic and harsh shadows as well. The background for the most part is very dark. That is your contrast and if you lean into it and exaggerate it your piece will have that depth you are looking for. With the light, think about the planes it will hit and use your brightest highlights there. Also think about anything that is being blocked from the light (behind the fingers, the folds, if a surface rounds away from the light like the cheek, it will start to have a soft shadow like a sphere light with one bright light) This goes for the eyelids, under the brow, etc. The fingers will cast a sharp shadow on the water as will the rock. You can practice looking at still life references to see how a bright lighted scene creates that sharp contrast and practice using just black and white to create your shadow and light shapes. Then gradually add values as you become more comfortable. Hope this helps give you some things to practice and some ideas to use on your next piece.