-for this I have used Gimp2.8 and G’MIC 1.7
1.Create a new image at 1024px by 1024px.
2.Filters -> Render -> Clouds -> Plasma with Turbulence 5.0
3.Filters -> G’MIC -> Black & White -> Hard sketch with following settings
Done! Play around with different starting textures and filter settings, you can make a wide variety of scratches.