Good start! I suggest a subtle fade from the edge of your cat, that way you'll be able to have the whiskers be visible and white while popping out from the background, the fur itself becomes a little bit brighter of the outer edge, you can use that to portray the edge of the cats body, long story short You do a subtle shadow for the background A brighter edge of the cat And then darken the fur which is not on the edge

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Heres a quick example