When you talk of Grunge Photoshop Textures you will notice that you cannot exactly define the grunge texture. But, the best thing is that the photos that are
overlayed on it look beautiful with their prominent features accentuated. The one that you choose for you must be high resolution and high quality so that it does not show grains.
The downloadable grunge texture available on the internet should allow you to photoshop in the content for textures. This will help you get the right kind of effect and the best quality image for your photo without having to undergo mush hassle.