Vignette, in past discussion, had a few possible approaches.
Approach 01: which was accepted, used a black-only vignette. The vignette uses a slider for intensity/transparency and has fixed geometry.
Approach 02 (simplest upgrade): Still use a slider for intensity/transparency, still use a fixed geometry, but give an option to select what COLOR the vignette is. The color we would most often use (besides black) would be white when fading out to white media or backgrounds.
Approach 03 (more complex): As was suggested, use an image as an overlay. Still use a slider for intensity/transparency. Among other benefits, this would allow the user: 1. to change the shape of the vignette (ie. more masking on the image sides) 2. add foreground effects such as rain or snow.
Cheers from the Midwest USA.