RE: Carl Design -
Besides his face being a tad odd (he looks kinda like he's got some strange grimmace going on... I expect bees to fly from his mouth or something)
There does not appear to be a reliable light source on Carl. I see a shadow to the side of the zipper, but I don't see shadow anywhere else on him. This combined with the width of his top-coat make him seem too wide (Not even fat, just too large, like his chest has been stretched)
I can kind of see shadow on the metal plate (above the zipper) but it's subtle. Sadly, I feel you should magnify that shadow as since there is no actual depth to the work, you still need to really push the perceived depth and better use of shadow should help that out quite a bit.