Halloween face painting idea 1: pumpkin
A    bright orange pumpkin painted on each cheek.  Black paint used to  paint   eyes, nose and mouth. A light grey would be  used to show the  ridges of   the pumpkin as well as its outline.
An  alternative would  be to do a   full face pumpkin with an orange face base  (blending a  darker orange   shade over cheekbones), black triangle shape  over the  eyes (extending   above and below the eye area), a black nose and  a  large black mouth   (need to cover more than just the lips).
Halloween face painting idea 2: skull
A    full face design. Has a white face as the base,  large black 'panda'    eyes, black and white vertical stripes on the lips  (with the white    stripes wider than the black ones) and a trickle of red  from one side    of the mouth (to indicate blood).
Halloween face painting idea 3: vampire
A  full   face design. A white face base, bright red  lips, fangs coming  out of   each corner of the lower lip (outline is light  grey, fill is  white,  and  tip is red to denote some blood), eye lids are  smoky grey  (right  up to  and over eye brows), eye brow then exaggerated  with  black  sweeping  strokes.
Halloween face painting idea 4: bat
A    full face design. A white face base, bat's face  painted on forehead    above the nose (it's in black with light grey for  eyeballs, and for    some definition in ears); the bat's body is painted in  black on the    nose and ends at the base of the nostrils (use different  shadings of    black; the bat's wings extends out from head and body and  covers the    eyes curving up towards the temple and down the outside of  the eye to    mid cheek (again use different black shadings and some fine  dark grey    strokes to paint some definition into the wings); the lips are   painted   in dark grey with an exaggerated upward curl at the corners.