From the same 'meetthegimp' thread as the previous poster, patdavid, but my version is sufficiently different to merit a post of its own, I think.
Should work in Linux and Windows and have a few more options so had to rework the dialog to barely fit on my Windows portable!
The initial idea of making this plugin, because my desire creates the brush strokes of oil paint style that resembled the actual painting. Manually inspired extra brushes and pens from gimpainter, there we can arrange the use of the brush patches digimpainter, seemed to conventional painting. Because we can adjust the brush pressure, brush types, we like mixing oil paint on our canvas. Examples of the use of the brush you can see in http://gimpmodify.blogspot.com/2012/03/mixbrush.html
This is 2nd version of very simple script. It creates image's borders.
To install this script:
1. Download "BW-border-ENG-v2.scm" file.
2. Copy this file into "C:\Program Files\GIMP 2\share\gimp\2.0\scripts" directory.
3. Script is in the "Script-Fu->B&W Border... v2" menu.