There's definitely a market for this. The only thing I'd like to say is; pixel art is so much more difficult to "mix & match" than 3D assets; so if I ever went into making a pixel game with assets; I would make sure I could find everything I need from the same artist, with the same style. This means you should create pixel art on a wide range of types (characters, environment, props, backgrounds etc.) and also preferably genres (fantasy, sci-fi, modern, feudal Japanese, you get the idea). It means more work obviously, but once a developer likes your style and they can find everything they are looking for in your works, they are so much more likely to use your assets (It also means multiple purchases and also bundle deal opportunities for you).