the last two ones look pretty strong, they seem inked.
I think another thing is your shadows dont really capture the shapes in the earlier ones, they focus on each bump and ridge instead of the overall shape of the object.
its like your coloring usually brings the feelings of relief sculpures... ex
instead of a full volumed object like a complete sculpture
i think if your greys had that 3d feeling they'd work really good like the one with the lizard dude, and some clean finish(inks?) like the last one.
In any case you seem to be getting better, hotness