Merge video and (re-encode) audio into single file
ffmpeg -i video.mp4 -i audio.wav -c:v copy -c:a aac output.mp4
Merge video and (replace) audio into single file
ffmpeg -i video.mp4 -i audio.wav -c:v copy -c:a aac -map 0:v:0 -map 1:a:0 output.mp4
Merge image and audio into single file
ffmpeg -loop 1 -i image.jpg -i audio.wav -c:v libx264 -tune stillimage -c:a aac -b:a 320k -pix_fmt yuv420p -shortest out.mp4
