Nope, it's completely fine to use this as your avatar. :)
k do u suggest i choose another avatar pic?
Looks good, but needs quite a bit of refinement before this will be accepted as "finished" into the gallery. Our reason behind not accepting pieces like this is because the definition of pixel art is fairly strict, and we'd like to keep Pixel Joint pure and avoid work that doesn't take any advantage of pixels. If you have any questions as to why this wont be accepted into the gallery (And be sent back for revision), feel free to PM me.
My suggestion is you take this into the WIP section of the forum to collect criticism in improving this piece and yourself as a pixel artist.