ffmpeg fade in from center (with scale image)
Use

ffmpeg -i file.mp4 -i image.jpg -filter_complex "[1:v]pad=iw*2:ih*2:(ow-iw)/2:(oh-ih)/2:c=black@0,zoompan='1+on/125':x='(iw-iw/zoom)/2':y='(ih-ih/zoom)/2':d=125:s=WxH,format=gbrap,fade=t=in:d=5:alpha=true:st=0[im];[0:v][im] overlay=x=10:y=10:enable='between(t,0,5)'" out.mp4

The image is padded to double width and height with the padding colour being transparent black. Then zoompan is used to zoom in over 125 frames (5 seconds). This result is overlaid on the video.

You have to replace W and H in the zoompan filter with the dimensions of your image.