Lithophane should work, you just need to make sure your background is pure black, and set thinnest layer to 0 in Lithophane model setting, and set thickness to whatever thickness you want your silhouette to be.
You might want to make your image black and white in photoshop by change your image mode to grayscale in photoshop, then use image-adjustment-levels to remove details of your image so that the final image have only two color, black and white and no gray at all.
You can download photoshop CS2 for free in adobe website. It is very outdated version but more than good enough for this function.
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