Here is a quick idea on making a selection and then using it mirrored to make a pattern.

First we have our image.  I am fascinated by graffiti and took this picture in Europe in 1998.  So we start with our train.

A selection is made of just the graffiti, you can do this with your favorite selection tool.  I used the pen tool in Photoshop CS5

Once I get that far I copy and paste to a new layer.  Then I copy and paste to another layer so you have 2 of the exact same image on the layer.  You can also use the short cut of command j for the Mac or control j for the pc

I turn off the eye on the train layer, go to canvas size and increase the width of the canvas to twice it’s width.  Flip one of the image selections horizontally and pull it over on the canvas to mirror the other side.

Then if you want a bunch of them, crop to the edges or the image and save.  In Photoshop CS5  go to Edit>Define Pattern and name the pattern if you want to in the pattern palette.

From there open a larger file to to Edit>Fill and pick your pattern to fill your space.

I’ll do a couple of other patterns in a few day that will fill the space with no white.

Patterns are a great way to show texture on layers of images.  I’ll post some of these ideas in the next couple of weeks.