To view the randomart image for an SSH key:
ssh-keygen -lv -f path/to/key
Example:
$ ssh-keygen -lv -f .ssh/my-fake-key
2048 ce:52:d4:22:8c:b6:a0:3f:e9:16:48:a5:87:b5:3b:1a chris@DEATHSTAR-3.local (RSA)
+--[ RSA 2048]----+
| |
| o o . |
| * + o o . |
| = = . o . |
|o.. o S |
|.E.+ + |
| *.. . o |
| o.. . |
| .. |
+-----------------+