Hi. New here too.. trying to help in someway...
Maybe you put too much dither.. I'm not sure, but I think the dithering is best applied on larger surfaces to work on the color transition.
Also, you could try to erase the two top pixel of the sides of the piano.. they are too sharp to my eyes..
Maybe some highlights in strategic pixels?

Hi everyone! I'm new here and new to pixel art too. I have this study group for a future indie game developing group, and I'm working on the 2D art. So, after reading a lot of good materials and some tutorials about pixel art on the internet, I've made my first original character that I'm planning to use in some platform game tutorials. I spent a lot of time to reach this point and it is really the best I could do. I would like some tips, specially about the palette and the shadow/lightining. What improvements will work better? I think I'm satisfied about this right now to begin with, but I really fell that I need some tips of experienced pixel artists in order to go on to the sprite animation.
tks!