Ok before you say anything, consider this, I am using other peoples brushes only because I have lost my own. Also, this tutorial is meant to for people who want it simple and easy. So don't go blaming me for it not being "good enough" or some other lame reason someone seems to point at me. So without furthur ado:
First off open up PhotoShop (CS?) and create a transparent document of a width of 450 and a height of 120
First layer: Filter -> Render -> Clouds
http://img107.exs.cx/img107/1609/aaa3du.gif
Create a new layer, download this brush. and load it.
With your newly created layer, brush evenly with black using the Crown__s_Fractals brush
http://img107.exs.cx/img107/2060/aaa27rt.gif
Create a new layer, download this brush. and load it.
With your newly created layer, brush evenly with white using the RoD_Inc___Render_Brushes brush. Set the layer mode to Soft Light.
http://img153.exs.cx/img153/7919/aaa34jd.gif
Create a new layer and take this picture (Tutorial Link Here)
http://img69.exs.cx/img69/1594/grunge4ep.gif
and add it to the layer and set the mode to Soft Light
It should now look like this:
http://img153.exs.cx/img153/9271/aaa41jt.gif
Now click this button http://img47.exs.cx/img47/7874/untitled22pq.gif and click Colour Balance
Mess around with the settings, I used
Midtones: 0 +60 0
Shadows: 0 +27 -31
Highlights: 0 +19 +55
Now your done your grunge-like background! This is my final result:
http://img173.exs.cx/img173/8658/aaa69iv.gif
Post your results!