In this tutorial I am going to show you a simple way to create a image to vector effect using any photo/image/graphics/etc. In the next tutorial I am going to show you how simple it is to turn from photo to vector shape in Photoshop. So let's start with this girl stock image; you can use any image you want but if you want to create vector silhouetts the best are the photos with white/black background. Or better still you can use cutout images.
Duplicate this layer and call the layers Girl 1 Layer and Girl 2 Layer. You can also keep a copy of the original layer. Go to Image>Adjustments and use the Threshold adjustment for the Girl 1 Layer. Set the level depending on your photo size, details, etc.
Set the foreground color black and the background color white. Go to Filter>Sketch and use the Photocopy filter for the Girl 2 Layer.
Set the blend mode of the Girl 2 Layer to Multiply and merge the two layers.
Use again the Threshold adjustment for the new created layer.
For a smooth edge result you can go to Filter>Stylize and choose Diffuse
This is how you can convert image to vector effect. You can now use the Paint Brush, color black to close the gaps and to use the Paint Bucket Tool if you want to add color. I have also added a vector sunburst using these free sunburst brushes to create a vector comics background. A similar technique I have used in one of my oldest tutorials on how to create a comic book effect in Photoshop
Go to - Convert to Vector in Photoshop
Custom Shape Creator - Make Vector in Photoshop
This set contains 1 layerd PSD file that will allow you to create a vector shape silhouette out of any photo/graphics/image. The pack also contains a Photoshop action that you can use to create custom shapes.