Cool idea and I like the colors and textures here. I think that all this recent talk of light boxes on the forum is giving you the wrong idea though. A light box is mostly for product photography where you do not want shadows and this image would definitely benefit from the use of light to create shadows. For example 90 degree lighting helps to create texture and would help the moss and wood plank be more defined. 45 degree lighting helps to define shape and would help give shape to the actual door knob. I agree with Sephibox regarding the focus as well. A more angled or lower point of view would give your door knob more 3Dish-ness. Right now it is rather flat. That angle of view would probably allow you to do selective focus more effectively as well. I think you have inherently all the ingredients to make the photo pop, you just need to work them a little differently.