Add image above the video with ffmepg
The basic form will be

ffmpeg -i video.mp4 -i image.png -filter_complex "[1:v]scale=320:-1[top];[top][0:v]vstack" output.mp4


A label of the form 1:v, equivalent to 1:v:0 within filters, is a stream specifier - it means use the first video stream of the 2nd input. 0:v refers to the first video stream of the first input.

The bottom in your command and top in mine are arbitrary labels assigned to the result of the scale filter.

Then that resulting stream is fed first to the vstack so that it gets stacked on top.