this can apply to many different situations, and looks different every time you do it, so if it turns out crap, do it again.
Its easy:
1. get your image. I used a sig:

2. create a new layer.
3. choose your colour. your background should be either black or white, depending on your colour. if its light, black, and if its dark, white.
4. Go to [Filter]->[Render]->[Clouds]
it should look something like this: (I used green)

5. Go to [Filter]->[Distort]->[Glass]
Distortion: 5
Smoothness: 3
Scaling: 100%
(These are just basic figures, feel free to play around)
it should look something like this:

6. Go to [Filter]->[Artistic]->[Paint Daubs]
Brush Size: 8
Sharpness: 7
Brush Type: Simple
it should look something like this:

7. Go to [Filter]->[Sketch]->[Plaster]
Image Balance: 20
Smoothness: 2
Light Direction: Top

8. change the layer type to Multiply or Screen, then move everything around untill you find a position you like. Add some text and you have:
Final image:

what do you think?