Nicely done set here. Small resolution but apple is very juicy and skull vert readable. The overall image has 261 colours, but I'm accepting this, becasue it seems, that each item has it's own palette, so it gives around 15 colours per piece. Have that in mind in the future, when making such compilation. Also consider reusing colours between the individual pieces. It always look better in game when items share the same colours. Most of the reds used in the apple, potion, ruby ring, etc. are very similar so could easily be unified.
I agree with gawrone - though of course it's a question of taste.
As it stands this has a visual similarity to the noisy pixelart style popularised by minecraft, but at this scale I think you could achieve far more visual interest by radically reducing hte palette.