judging by your work your boxes are not that bad i like how many differnt kind of perspectives you did.But there are still some mistakes first one when you shade your box make sure you visulaize from the viewver perspective on what he will see because when you shaded some of your box they dint match from the viewers eye.Also another thing some of your lines dint meet up to the perspective some lines drift to completely to one side then other just make sure you visualize your lines before you make the line.But these mistakes are bound to happen so overall nice boxes.