Its a good first(better than mine) but there are some general rules to spriting that yo need to learn
First you always want to make your border lines no thicker than one pixel, thats the part where yo trim it down.
Next you always wan. To make the border lines the darkest shade of the color your useing on the sprite(black makes it look not as realistic) and i dident get a good look at shading but i think you know the shading rules. All in all good for a first, it will need some more work weather its you or me before its ready for the game.