Hey, these are all pretty solid in terms of getting the idea across. My one critique is that I think your sketches could benefit from more contrast and lighting. For example, in that toaster sketch, the values of the top, right, and front side are all pretty similar. Pick your light source direction, which tells you which side is going to be the brightest/medium/darkest. Shade each side accordingly. If you're using markers, you can literally pick out 20% gray, 40% gray, and 60% gray, and use one for each side. Then add the more detailed shadows around components, like the knob, for example. I hope that's helpful! Keep it up.