I tried my best with this tut.
1. I always start with size 350x100 pixels and white background.
2. Press D to restart your foreground and background color to black and white
3. Go to Filter > Render > Clouds
4. Then go to Filter > Render > Different Clouds
5. Go to brushes and pick brushes number 39 then brush it a bit not too much
6. Go to Filter > Distort > Ocean Ripple, then set 15 in Ripple Size.
7. Go to Image > Adjustments > Hue/Saturation and click on colorize and choose any color what you want (in Hue) then use saturation and change it in 46. Go change Lightness in -18
8. Then go to Sharpen > Sharpen Edges 2 times.
9. Your image should look like this...(your may be different in color)
10. Your finished but you can add text/render if you want
Your done with signature background, it can be in any size.Hope ya like it.