Great work, especially the rifle and headphone. I do have some crits though, on top of what others have said:
Desk scene: You shouldn't be able to see the label on the inside of the pill bottle. This could be fixed by either changing the position of the bottle so you can't see inside it, or (better) giving it a double-sided texture, the inside texture being the colour of the bottle without the label. Also, the lamp base and shade is a bit too low poly. Maybe consider subdividing.
Rifle: Great work, nice materials, excellent model. I don't know if the timber backdrop is an object or a background, but if it is an object, I would re-render the scene with soft shadows falling on the timber, which would place the rifle physically "there". At the moment it kinda looks disconnected from the tabletop on which it rests.
Cannon: For a quick project it is quite good. The flash from the muzzle does indeed look like an anemone, maybe useful if you ever do an underwater scene!
Headphones: Lovely work, again great materials. Maybe a little more lighting to show off the textures of the ear pads and microphone cover would be good, and again I would consider subdividing the ear phone shells. They look a little steppy, which detracts from an otherwise excellent model. Without those steps, this could be a photograph.
Great work! I particularly like your attention to detail and sensitivity to textures and materials. Keep posting, it's good stuff!
