See through text

A clipping mask allows image to show through text - or graphics

A clipping mask lets you have images showing through text or graphic shapes.
This has three Photoshop layers - on the top is a photograph of a sunrise. Below it is a text layer. Below that is a simple white layer. 
Look at the layers palette. Layer 0 (the sunrise photograph) has a small arrow - this means that it is clipped to the text layer. The image is showing through the text. You can set the clipping by ctrl-clicking on the picture layer.
It works with text, so it also works with other vectors, like custom shapes and brushes.
Simple - try it, play with it and experiment...