The characters are really good, the black one specially. However, you lighting is kind of weird, is not bad, just misused. Because is too bright at the top, where there's nothing going on, and where your characters are, is just too dark to distinguish them. You almost had it, adding the lights to the head flippers thingy. But you made the mistake to place that part (the head) where the background was also bright. So yeah, just keep your values in mind, make your focal point have more contrast. Keep that in mind and the quality of your work should improve amazingly, because is not bad now, but it could be better.
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