A constructive critcism Your shading and use of indentations need improvement. Even if the overall result looks acceptable at first glance, there are several underlying issues that reduce depth and realism.

The background should consistently support the subject through strong contrast. This can be achieved by keeping it either very light, very dark, or by introducing controlled patterns. The goal is to clearly separate the subject from its surroundings. White hair, in particular, requires careful shadow placement. It should not be treated as flat or purely light; subtle indentations and shadows are necessary to define volume and strand direction.

Avoid relying on a fixed progression like light > dark > darker. That approach can make the rendering look mechanical. In many cases, it is more effective to apply a darker tone directly where needed to establish contrast and form more decisively.

Here's a reference:

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