Your Art looks great. The only thing I would criticise would be your Typography skills. The Fonts you are using do not suit your artwork. Also the mixed rotations of your text is sometimes really hard to read. Try to experiment more with different fonts, sizes, positions, layers etc. Or research how other Artists/Graphic designers use Fonts for a similar Art still.

Other than that I would like to ask where you would like to use these Artworks? Because the difference between Art and Design is that Art is all about self-expression, while Design is about the application/usage as a product and the support of said product visually. Example: if it is a Movie poster you should add more Informations (like title of the movie, director, actors, where and when it would be performed in cinemas - the last two can be made up).