I'm not an expert at Pixel Art, but from what I've seen from your works, you need to begin to perfect your curves. On some they can be quite jagged and it really detracts from your attempt to make them somewhat 3D. One thing I really love about your work however, is that scenic piece. It's excellently done, so good job on that. I think will a bit more practice, you'll begin to grow into a good Pixel Artist!