Your artwork is amazing!....i really dont have any advice to give!...my advice based off the photos i saw are to practice shading and establishing value in your pictures! Did you ever study proportions at all?
If you wanna get better at landscapes I suggest practicing perspective (much like the hallway drawing you did) and drawing 3 dimensional buildings like clock towers or skyscrapers. The same goes for still life drawings. You can use the same method in the figure drawings. Draw through the object, build it up like you do a figure. Landscapes can be exaggerated too. Don't be afraid to push the boundaries of the subject.
I noticed your very good with characters and figures. Try building environments for your fantasy/cartoon drawings. You have a great cartoon bird, try putting him a location that reflects his character. For instance put him in a nest. The nest could be huge with a bunch of other birds in it or it could be super small and he can barely fit in it.
The setting is a character and is just as important.