I came up with this technique when I very first started making textures. Instead of making textures from scratch as I've showed you, we're going to make a texture through photo manipulation in PS (probably can be translated).
Inside the Mirror
We'll be going from
to
Crossposted to :
icon_tutorial #1
Start by taking a random stock photo (anything you can find for free through Google...or take yourself) and crop it to 100x100.
#2
Duplicate the layer.
Filter>Pixelate>Mosaic (Cell Size: 8)
Set to Darken
#3
Remember what we did in the first tutorial? Duplicate the whole thing multiple times, move the layers around in different places, and set them to Screen.
#4
On a new layer, Fill with this pattern and set to Linear Burn at 50%
#5
Using different brushes (I use Photoshop's Wet Media brushes), on different layers, set to different opacities, with different colors, doodle. I set the darker ones to soft light and lighter ones to Screen.
#6
Add this gradient as Exclusion at 30%
#7
Add this gradient as Screen at 100%
#8
Add this light texture made by me and set as Screen.
Final
Example