I’m guessing it could be done by plotting B.Cu to a file, processing it suitably, then adding to F.Silk as a graphics object. Has anybody experience in doing this?
Export, processing in some other program and re-import as graphics is the obvious workaround. On your photograph the fill also clears other silkscreen items.
In KiCad copper zones can already have a fill pattern. The most logical implementation for KiCad would be to have a fill pattern for polygons. Is that a useful feature, or fancy decadence?
I think I have seen this used on single sided FR2 power supply boards. It does make fault finding a bit easier, because you’re not getting confused by the mirror image while looking at the back. But these days, it’s just so easy to make a few photographs, mirroring and overlaying them in some graphics package and then magnifying the whole thing on your 107cm monitor and making notes while working on some PCB. There are so many options these days…