First off- the sketchiness and use of more traditional are style brushes is very well thought out. I really like the shading as well, which isn't something you can get just by drawing over a reference. The different textures also work well to make it look more like fur than just digital brushwork.
The only reason I docked points for originality is this is a practice work, as was mentioned in the description. It's honestly a very good piece and I feel like could be a very good finished piece.
This is a very good start all said and done. Great job!