I'm absolutely blown away by these organic environments you have in this sketchbook. Some are very Turner like, if you check out his work i'm sure you'll find some inspiration or at least a person to try and beat! Haha.
Even your environments you called generic are full of atmosphere and capture the feeling brilliantly. The caves for example lead me to wonder what's around the corner, what's coming, who lives here and all these questions which are relevant to concept related art. I could totally see you creating environments for space / sci fi related comics.
Your people haven't been that impressive though, mainly because you a) haven't shown very many, lol and b) because you are still learning.
There are definitely great things to come from your art, especially when you are able to convey decent people in your environments, man that's going to be incredible. In fact the environments you have with people in them, say the guy with the tube or even the red guy against a white background, are still interesting to look at. Maybe as a way to improve you could start off with small figures in your environments and then as your people improve gradually make them bigger in your environments.
The jungle, hall way, lake with birds, recent mountains.... All amazing. In fact anytime you draw trees near a lake, I pretty much stare at the picture for ages. Your environments are your biggest strength right now, so learn what you can about drawing good landscapes, it will improve them even more. Hence why I suggest Turner. Maybe divide your time between organic environments and anatomy, say fifty fifty or eighty twenty, because the emotion and feeling of your environments is something that would be sad to lose.