procedurally generating a texture overlay simulating shrink wrap
I finally arrived at a solution that is not perfect, but seems to be good enough for my application right now.

The pipeline is as follows:

-&gt; grayscale perlin noise with affine transformed (stretched and rotated) coordinate system
-&gt; gaussian blur (sigma 3.0)
-&gt; normalize (range 0.0 to 1.0)
-&gt; pixels = pixels - 0.5
-&gt; pixels = pixels * 2
-&gt; threshold (change everything below 0 to 0)
-&gt; add pixels to original image with an alpha value of 0.7


Here are some of the results: