Age has very little to do with artstic skill, im 27 and having been drawing most of my life and im not as good as you are...
so that being said I really like your work. I was a bit worried when I saw the anime work but you also did a good mix of background/building and other style, its easy to get fixed on one style, dont do it!
Your work being so nice you should do some on a tablet for digital art
after all having your own artwork in a game you made is a cool feeling.