Great artwork! I love the atmosphere (: All of your concept arts are amazing and I hope it's okay to ask you: What do you use for Brushes and what are their settings? Do you have Tutorials? And do you work sometimes with references or something like that, because they're looking really stunning Go on like this and have a nice week (:
Until you feel completely comfortable painting with the circle brush, I wouldn't reccomend looking for fancier things. Brushes don't make good paintings, skill does. You won't build skill if you set yourself up to be dependent on fancy brushes to do the work for you.
That being said, digital artists frequently post their brushes for download online. Here are some very useful textured brushes from ~djahal : djahalland.com/ go to "goodies"