feh has a index & montage modes, where it reads multiple images and displays or creates a single image containing a grid of thumbnails with all the images.
The man page has this example:
feh -irFarial/14 -O index.jpg /opt/images
Make an index print of /opt/images and all directories
below it, using 14 point Arial to write the image info
under each thumbnail. Save the image as index.jpg and
don't display it, just exit. Note that this even works
without a running X server
If you've got libreoffice installed you could try these:
feh -i -O index.jpg /usr/lib/libreoffice/share/gallery/www-back/
That creates an index with names of all the files. Or the following will open feh viewing the thumbnail image, but with no names:
feh -m /usr/lib/libreoffice/share/gallery/www-back/