Applying textures to photographs has become incredibly popular over on Flickr and it is relatively easy to get the hang of. They can pull together an image tonally, add atmosphere and even hide dodgy photoshopping (especially useful if you're using a montage of images). I do fear that a few authors have discovered the concept and are using it to poor effect, hopefully these tips will shed some light on how to do it better.
So first up, I have a basic photograph with plenty of space for me to add text where required. I would like to point out at this point, do not use modern art on your cover without permission from the artist/owner (unless you have purchased through an image library). I'm using this bird sculpture for demonstration only and wouldn't use it in a final design. I've used a Lightroom preset on it before starting to adjust contrast and colour.
A texture for this purpose is simply another image that is applied over your photo using layers. There are thousands of free to use textures in the Textures for Layers Flickr group. These are all licensed for free commercial use so you don't need to worry about asking permission first. Do not grab random images off the internet. I have used two textures from that group, from here on known as texture 1 and texture 2.
The following shows the different blend functions you have with your layers (click on thumbnail for larger image). They may vary slightly between software but you should have equivalents. In order to try them out, paste your texture image into your photo image as a new layer (you may need to resize and rotate first) and find your layer properties toolbar.
Some of these are more useful than others and the effects with vary wildly depending on your choice of images, both bottom and top layers. I can understand why people might use exclusion, for example, for a quick, dramatic effect, but it needs to be used carefully and works best with abstract images. Mostly, it just looks like someone couldn't be bothered spending time on their cover. Once you've selected the layer property you can also change the transparency to alter the strength. There are loads of other things you can do with layers, but this is a good starting point.
I decided I quite liked the colour and saturation of it set to burn but that it lost some of the actual texture. Therefore I pasted another copy of texture 1 on top and set it to screen (at this point I merged the first layer down as I decided I was keeping it).
The bird's a bit washed out now so I got out my trusty eraser and deleted off the screen layer. This is a bit cack-handed as I did it in a hurry on my laptop touchpad and I would probably use a graphics tablet if I were to do things properly. However, as you might notice as I go through the steps, some of the messiness gets covered up. If you zoom right in, make your eraser small, and take your time, you will be able to do this neatly (or you could use masks if you're used to them).
Once I'm happy(ish) with this, I merged down the layers again in preparation for texture 2 which I only used partially (easy to do with hi-res images, just don't resize to the same size as your work-in-progress). Once again, I copy and pasted as a new layer and this time changed the layer property to multiply. I also changed the hue/saturation/lightness of this layer to be a bit closer to the colour I'm striving for.
It's starting to look more sophisticated, is it not? Already, it's harder to notice the bad edit on the bird (not that I'm endorsing sloppy editing, but I know you're not a skilled designer if you're reading this). I'm done with the textures now so I'll flatten the image but I feel I've lost some of that warm glow I liked in the first instance, so I added some contrast using curves.
Time to add some text! I'm not entirely happy with my choice of font, I'd like to spend more time finding something better suited to the overall feel but as my fictional book doesn't exist (and I'm running out of time here), this will do for now:
And because I'm never happy, here are some different versions once they've been through a few Lightroom presets.
Whilst my time is limited, I'd love to do a few real cover makeovers as part of this series. Please get in touch if you'd like me to have a bash at re-designing your cover!