Two videos on image background
I managed to solve this after some pondering.

ffmpeg -loop 1 -i Image.jpg -i Test1.mp4 -i Test2.mp4 -filter_complex "[2:v]tpad=stop=-1:stop_mode=clone[v2]; [1:v]scale=640-20:360-20[a]; [v2]scale=320-20:180-20[b]; [0:v][a]overlay=10:(main_h/2)-(overlay_h/2):shortest=1[c]; [c][b]overlay=main_w-overlay_w-10:(main_h/2)-(overlay_h/2)[video]" -shortest -map "[video]" -map 1:a -vsync 2 Output.mp4