Alrighty hun let me try and help you out here. You have a good basis for your design, but overall, its very plain and one dimensional.
The base coat should be a variant of different grey shades, even for a solid. A rabbits undercoat is generally lighter, and in this case would resemble much more white along the throat and stomach. Adding black into the outer parts that line the rabbits spine would also help.
As for the mottling of frost tips along the fur, you can see from the picture that the hair is also black tipped as well. Adding some black speckling as well as different grey layers should get the same effect.
THe stationary scattered pen pricks looks fairly drawn on, which dosnt work when youre going for a natural look. Hair dosnt stick straight out from the body, but rather lays flat and runs along the contours. To get the same effect, using the smudge tool and lightly dragging it in the directions the fur would lay just slightly can help resemble a fur pattern.
The nose and inner ear are also very flat and one dimensional. Just some simple blending with various base colors could help that.
Lastly, where the white pattern meets the base coat is somewhat sloppy. Blending the edges like you did is fine, however it should line up with the lines on the back foot and actually blend into the fur for the front feet.
Hopefully thats helpful? Let me know if you dont understand any of it ^^