gruhmuhfurrn
:U
Great to see that you're having fun with what you're doing, because that is THE IMPORTANTEST THING. Gonna be honest with you though, you need more practice. At least you're not doing pillow shading, so that's a good start. :v
Your pencilthings are actually pretty good, so i'll focus on the spritey things:
THE SHADING. Try practicing with some basic volumetric shapes before going big, such as cubes, spheres and cylinders. It's great for building up your sense of space, which is EXTREMELY USEFUL for arting. Then, once you have that down, try to see how the things you draw relate to these forms. For example, a grammophone's speakerthing is just a bent cone, so it'll have shading similar to a cylinder.
THE LINES. While you "only" have a mouse to work with, try not to depend on it too much for free-hand lines, because mice are TERRIBLE for free-hand drawing (speaking from gruesome experience). It can be used to set up a sketch, but be prepared to manually clean up the lines afterwards, because raw mouse lines rarely look good.
This particular tutorial covers the most common pitfalls, and then some.
But basically, the most important thing is to keep at it. Checking out tutorials like the above isn't a bad idea, though obviously (and sadly) they're not like magical skill boosts. :v