A few points:
-It has no apparent neck, and the head is very seperate from the body. In the best case it looks like someone wearing a mask.
-Related to the above, the amount of body we see for the front and side views is in both case 16 pixels high, but the head in the front view partly obscures the shoulders. Assuming the front sprites are viewed slightly from above this suggests that the front lizards are higher than the side ones.
-The head spikes are much more pronounced in the side view than in the front view. You also seem to have some readability issues with them in the front view, which you can resolve this by letting the spikes sway to the sides a bit.
-The portruding jaw on the side sprites is not evident on the front and back sprites. I'd suggest adding it to the missing ones rather than removing it from the side sprites, since it'd add some more form to the head. It'd just be an egg otherwise. Where the jaw connects the shading doesn't make much sense, and that bit seems pillow-shaded.
-Speaking of pillow-shading, the shirt and arms have that too.
- The eyes don't make much sense to me. The front view suggests that they more or less follow the rounding of the head, yet the side view suggests that the eyes are more on a forward facing plane. You could make that more apparent through shading.
-You should continue the scaly texture in the darker parts of the sprites. It's most noticeable one the back view's head.
Also, you don't have to watermark the image I think. It seems a bit pointless.