Ok this is my first tut so it probably sucks but well lets give it a go:
1) Download Grunge Brushes :P (the most important)
Just search on google... ->
angryblue ->
deviantart (Install them in the map Photoshop -> Presets)
2) Now make a new image...
And set the colors like you want
3) Its always handy to use Filter->Render->Clouds first...makes it looks nicer
4) Make a new layer
5) Grab the Brush Tool and click on the (blue) round button with the little arrow on it. In that menu select the grungebrush you just installed :)
6) now play around with the brush with a light color....Dont make it too full

(img is without the filter>render>clouds behind it!)
Looks a bit like this but it is different bcause you prob. uses different brushes...
7) Make a new layer
8) Now use a darker color on this layer and play around with brush again!

I used a special brush on this one but cant find the site anymore :S and it
is too big to attach :S
9) Now you can add the Images and the Border.....
(any questions just ask)
My final result
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