This is my entry for the Jack o' Lantern challenge. I simply took the given template, drew a bat symbol in Inkscape which I imported into 123d design. Then I resized and extruded it the desired amount and subtracted it from the Jack o' Lantern. I have uploaded screenshots both with and without outlines to give you a better view of the 'hard to see' sections of the model.
Runner Up in the
Make it Real-ly Scary with 123D and Tinkercad Contest