Create a Non-Destructive Vignette Effect with The GIMP

If you would prefer a patterned background for the vignetted photo, select a pattern from the patterns dialog, then go to Edit > Fill with pattern.

This vignette is non-destructive because none of the pixels in our original photo have been changed. You can reveal the entire photo again by right clicking in the layers palette and choosing "Disable Layer Mask." You can also modify the vignette effect by further editing the mask. Try toggling the layer mask off and on to reveal the original image.