|jack-o'-lantern from wikipedia|
I am posting this separately, because many people start with general searches and get drawn into offers of paid images when this may be completely unnecessary for their projects. I would suggest looking at wikipedia first. For instance, 'Halloween clipart' google search will give you 2,5 mln results, but if you look at wikipedia articles on pumpkins and jack-o'-lantern you may find that the images accompanying them are suitable for your project.
Read the general overview on where to find clipart for Macs and see other posts on clipart at the 'Clipart and Photos' tab above.
And see an example of how to use images from Wikipedia as clipart (magnifying glass) here.