The header image is based on ffmpeg’s testsrc video source. I then cropped it and added noise. I also used the swapuv filter so that the resulting colors are not typical for standardized video color bars as if a component video signal is patched improperly.
Here is the command to generate the image:
ffmpeg -ss 8 -f lavfi -i testsrc=size=850x480,crop=850:130,swapuv -ss 8 -f lavfi -i 'nullsrc=s=850x130,geq=random(1)*120:128:128' -filter_complex '[1:v]format=yuva444p,lut=c3=128,negate[out],[0:v][out]overlay' -map  -frames:v 1 header.jpg