Follow the instructions on the page of the above link for Béchamel Sauce; stir in a cup of white cheese at the end; stir until the cheese melts; set aside. When you’re ready to make the ghosts, thin out if needed using a bit more milk. Transfer the sauce to a squeeze bottle such as old mustard container or those used for melted chocolate.
Using the squeeze bottle of béchamel sauce, draw an outline of a ghost on the pizza and fill in with more sauce. Repeat as many times as the sauce and pizza allow. Quickly add on the tiny pieces to make eyes and a nose.
For a quick version but not as pretty, you may cut slices of Mozzarella cheese into the shape of ghosts and add to the top of your pizza. Melt the cheese in the oven. Once it melts remove and allow to cool for a few minutes prior to serving.
https://glutenfreerecipebox.com/gluten-free-halloween-pizza-dairy-free-options/