Not to sure where this image is going. Are you trying for a photorealistic look or something less real? If you are going for realism then there are a number of things to think through. The colour tones used are a bit varied, almost garish. The tree in the foreground has autumnal colours but the tree in the distance appears to be a cherry tree in spring. The water in the foreground to me is "travelling in the wrong direction" it should be flowing away from the waterfall but instead it seems to be moving at 45 degrees to it. If the image is set in autumn the grass wouldn't be such a bright green. What is the yellow blobby stuff? rocks? The spray and foam at the bottom of the waterfall needs to be more misty as its too sharp and defined. There are patches of yellow that appear in amongst the rocks and waterfall why? The rocks or is it sand to the top and left of the waterfall, would it really be such a different colour to the surrounding rock faces? The writing desk isn't convincing due to wrapping the timber texture right round the two visible sides. In reality the desk would be made with separate pieces of timber and a joint would appear at the external corner. The timber used to make the drawer. The direction of the grain is wrong and the colour of the timber clashes with the rest of the desk. Basically I would say you need to look more closely at how things work in nature and how things like furniture are put together. I'm sorry to list so many things that I see as a problem but hopefully you can step back and reassess what you are trying to achieve and make progress.