https://www.thedigitalpictureframe.com/the-best-3-image-viewers-for-your-raspberry-pi-digital-picture-frame-project/
https://man.finalrewind.org/1/feh/ - man
$ feh -qrYzFD120 –zoom fill /home/pi/Pictures/your-images
where:
q = quiet mode, r = recursive, Y = hide pointer, z = randomize, F = full screen, D120 = delay of 120 seconds and zoom fill = fills your screen.