I have been asked many times by PM and on MSN about this same thing and I have explained this on the forums as well. But people don't understand properly, so here is a quick tutorial for everyone who doesn't understand on how to have a picture inside your text.
Type in the text that you want to have,
Open up the picture that you want to have inside your text. Drag it to your text and move it over the text layer, now your text won't be visible.
This is the small layers structure at the moment, now hold down
ALT and
CLICK on the red highlighted area shown below.
An Icon will appear when you click over there and now your picture would be inside the text like this,
Grab the move tool and feel free to move around with areas of the image that you want to have inside the text...