I think one could make a good internet kiosk with i3wm... as in one could lock it up to a browser pretty nicely. I haven't done this myself so I will just generalise the steps...
1) Install i3wm, preferably on a distro with su. 1.5) Of course set it to autologin into the i3wm session. 2) Customize the config to launch your preferred browser on startup 3) Comment out all keybindings of the i3wm config that are not needed. The only keybindings I would keep are the fullscreen toggles and dmenu. 4) I would remove everything except gksu and the browser out of /usr/bin into sbin. So that even if a user discovers the keybinding for dmenu, only authorised users can reach programs other than the browser. Optionally for ease of administration a keybinding could be made that would launch a terminal via gksu. 5) Make a keybinding for shutting down the pc. 6) Once we are done with making the config, just for extra measure we change the permissions on the config so that only root can edit the i3wm config.
And I think that's pretty much it if all that you want is a locked down browser only internet kiosk. Optionally if you want the user to be able to use some other programs as well, then you just leave those programs in /usr/bin, perhaps make keybindings for them as well. And then you put those keybindings on a piece of paper.
Apparently the guys at suckless already did something similar: http://surf.suckless.org/files/kiosk_mode I personally as you can see would not do the exact same thing. But both approaches are fine, depending on your wants/needs.