The last version (2014071317) supports multiple image set and different type of images.
To create a second number of images you have to
a) go at Home / ► Site administration / ► Plugins / ► Activity modules / ► Manage activities
and in the Settings of Game
set "Number of image sets used by hangman" to 2
b) Go to parameters of game and sets the parameter "Select the images of hangman" to 2
c) Create a folder at the mod/game/pix/hangman with name 2
d) In that folder copy the files you want with names hangman_0.jpg, .., hangman_6.jpg
Instead of .jpg you can use .png or .gif