First of all you need many many textures, photos and all that stuff.
All sharp and over 1600x1200 resolution.
Then all you need to do is experiment with them, put one almost clear texture as the background, and then add many tekstures with overlay/soft light/ hard light. Erase what you dont want to and viola
Now only one thing is colour. Use dark colours but you also need some experiments

I hope i've helped you a little
Good luck

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PzyKrizz