Both Issabella and myself have finished our tests.
So, here is the filter:



GIMP plugin to create a drawing look using G'mic Engrave.
Inspired by a Nidhogg's tutorial posted on Gimpchat last year, but modified to create a Van Gogh style.
At the end of the process, the filter creates one or two (optional) layers, both masked:
- the first one created is a layer containing the yellow colour used by Van Gogh
- the second one created (thus, on top) is a layer containing the original image
If you choose to create them (options in the menu of the filter), the "yellow" layer is already active, because the mask is a gray copy of the original, the mode is set to LINEAR_LIGHT and the opacity to 50%. By this way the lightest zones of the standard outcome are "illuminated" by the Van Gogh yellow colour.
You may play as usual with opacity and mode, at your taste.
The "source" layer is created with a black mask, hence it's not active until the user paints over the mask with a light gray to determine the overlay of the source over the textured outcome.

First example:



-the Van Gogh effect applied is "weak"
-the yellow nuance has been applied, with a limited impact
-the face had not been "cleared" nor "smoothed" by overlaying the source

Second example (source from Deviant Art):



-the Van Gogh effect applied is "medium"
-the yellow nuance has been applied, with a limited impact

You will find much better examples by Issabella in the thread used for Experimenting this style