You could also create a very unique pattern in a new channel. Click OK . Depending on the complexity of the image the results will vary. You can also fill your pattern as a layer mask. You can produce some really cool effects by adjusting the Levels and Curves of the masked layer.
Some example are below.
To create the pattern effect used here, I created a new channel by pressing the Create New Channel button in the Channels palette. I then applied a clouds filter. I pressed the Load Channel as Selection button in the Channels palette, selected the photo's layer in the Layers palette, and clicked the Create Layer Mask button in the Layers palette. I then filled the defined pattern into a new Alpha Channel of the photo. Once again I pressed the Load Channel as Selection button in the Channels palette, selected the photo's layer in the Layers palette, and clicked the Create Layer Mask button in the Layers palette.