1. Open all your images
In Photoshop, open your portrait image and the textured layers you want to add. On your portrait, click Create a new group at the bottom of the Layers palette – in here you’ll keep all your texture layers. As default the blending mode for the group will be Pass Through, change this to Soft Light or Overlay, depending on the strength of the effect you’ll want.
2. Add your textured layers
You’ll want to add your textures to your portrait, one by one. Click on your first texture layer in the Layer’s palette and right click (ctrl)>Duplicate Layer> select your image layer to add it to – it should now appear on top of your portrait layer. Click and drag the texture layer into the new group folder. At this stage you can see how the texture interacts with the portrait.
3 Adjust the texture
At first you need to concentrate on how the texture affects the background, ignoring how it overlays on the person, so use the Edit>Transform tools to re-size, move and rotate the textured layer to best fit the look of the image. If the effect is too strong, you may want to reduce the textured layer’s Opacity slider or change the layer’s Blend Mode.
4. Adjust colour
If your textures are monochrome, repeat steps two and three for as many textures as you want to add. If your textured layer is coloured go to Image>Adjustments>Black & White to desaturate the layer before adding it to your portrait so as not to affect the image's colour. At the same time, coloured layers can affect images for the better if chosen carefully.
5. Reveal your portrait
Now that the texture is overlaid, you need to mask the texture so that it only applies to the background. Click on the image layer and using the Quick Selection Tool, select the subject. Click the Group layer and Add a Vector Mask icon at the bottom of the Layers palette to fill the mask with your selection. Press Cmd and I to invert the layer mask.
6. Finishing touches
If you want to blend the edges of the subject with the texture, use the Brush Tool set to White with a soft edge and low opacity. You can now focus on refining the look of the textures. You can reduce the opacity of the entire Group for a subtle finish or open the Group folder and reduce the opacity/change the blend mode for each textured layer until you’re happy.