Confirming the images are visible!
First and right off the bat, try not to use a black background for your sprites. It's hard to distinguish what is supposed to be part of the outline and what is part of the background, making the sprites choppy and messy looking.
But more importantly, every one of your sprites save the third one (which appears overly simplistic in comparison) have a lot of unnecessary pixel noise and misplaced color, which makes me wonder what methods you used to recolor these. In fact, they look like completely different people made them! Mind sharing how you went about actually coloring these and where you got your base sprites? If we knew more about your technique we could help get these sprites in order.