feh

I really like the image viewer feh.

Install with:

$ sudo apt-get install feh

And then use:

$ feh --auto-zoom --no-jump-on-resort --recursive --randomize --fullscreen --slideshow-delay 30 .

in your home directory to get a slideshow of every image you have.

Cryptically but more typably:

$ feh -FZzrD 30 --no-jump-on-resort .