New Static Prop head
Below is a how-to for transforming regular styrofoam wigheads into affordable monster, witch, or whatever face you want static prop head using a product called Celuclay, which is a paper mache type material.

Celuclay can be found at any arts and crafts store as well as Walmart.

A 5 pound bag runs about $25.00 or a 1 pound bag for $5

A little goes a long way with this product.

Keep in mind that this will make your wighead very heavy depending on how much Celuclay is applied to the form.

For lighter weight wigheads you may want to try Model Magic also available at the above locations.
Mix desired amount of celuclay with water .. mixture should feel like normal clay.. not too wet.. the wetter it is the longer it takes to dry so keep that in mind when mixing. Also keep a bowl of fresh water near by to keep your hands wet while applying.. this keeps the celuclay from sticking to you and helps to smooth out any bumpy or rough parts.
Any standard styrofoam wighead will work .. you may also use this on foam balls or beach balls or whatever .. this stuff seems to stick to just about anything.
You simply apply celuclay to the wighead forming the face you want. This particular one was going to be a goblin.
Once full face is formed allow to dry.. these took about 1 week to dry completely. I used glass stones for eyes. These were painted with acrylic paint once dry. A clear coat should be heavily applied if using prop outdoors.
Examples of finished products: