Brilliant.
Only complaint: a gibbet was for the display of already dead criminals, not live ones. These are all gallows.
I love the fact that you do additional damage if you hit them by mistake. I'd suggest that in a sequel (unless you already do this in later levels; I haven't gotten past level 8 yet), you put a hangman by the gallows and make the player shoot him first. Or heck, hangman and officials.
But art is great, gameplay is great -- only thing is that sometimes the placement of the bow is such that you can't get to full power without going off the screen; this may be intentional but it can be annoying regardless. Well done!