Hello,

To visualize the photos automatically using GnuPG on Ubuntu you need to edit your config file.

Edit:

gedit .gnupg/gpg.conf

If you want to enable the exhibition on key listing look for and uncomment

# Display photo user IDs in key listings
# list-options show-photos

If you want to enable the exhibition on verification look for and uncomment

#verify-options show-photos

Add this to the config file with the photo viewer that you want to use. In this case eog

photo-viewer "eog %i"

Save the file, and enjoy.
Matheus