Hi, welcome to Pixelation
Some attention could be given to the shading, particularly the highlight. At the moment it's following the rim of the sphere, which is inconsistent with how the rest has been shaded. Check out some example of spheres and how they are shaded.
Also a number of very similar colours that can be merged, and increase the contrast. You might want to make it fluffier... though that could be quite difficult without a specific background and at this resolution.