I've used glitter as an example in this post because it looks sparkly and eye catching, but actually you can use any sort of background image at all to make your fancy lettering. I recommend checking out this post on free background generators if you want to experiment with creating your own patterns.
Making Glitter Text Using Photoshop
Step two. Once your chosen image is open in Photoshop, you need to define the image as a pattern. To do this, go to "Edit" on the menu and scroll down to "Define Pattern...". Name your pattern and click "OK".
Step three. After turning the glitter image into a pattern, you will be able to use it for your text. Here I have just created a quick image with some text on it. You can use whatever font you want of course, but the thicker the font the better your glitter text will stand out.
Step four. Go to "Layer" on the menu, followed by "Layer Style" and then "Pattern Overlay...".
Step five. A box will pop up with all of the patterns you can use. Once you have selected the one you want to use, click the "OK" button.
Step six. That it is pretty much it! If you find that the text doesn't quite "pop" us much as you would like it to, try adding additional effects such as a drop shadow ("Layer"/ "Layer Style"/ "Drop Shadow").
I think that covers everything, but if you have any questions then please leave me a comment.
Free Glitter Textures
As promised, here are my glitter textures. You can use them for whatever you want (but personal use only please).