After looking through your latest work, I think you could work a little bit on your quality of line. In the first piece, it's confusing sometimes to understand the form. You could tidy up the lines a bit to make the drawing read better, as well as introduce clearer overlap and varying width of your lines to create depth.
The anatomy of the hand where the chap is holding up a mug feels a bit weak, I think you could do some further study of hands for this.
I like the perspective studies, I think these are my favourite, they read nicely as thumbs and this is a good sign.