1. Find a Good Particle or Grunge Brush
There is a website called Brusheezy.com which has a ton of great free brushes. Get over there and run a search for “Particle Brushes” and find a nice little particle brush set and download it. Save it somewhere on your hard drive so we can find it later on.
2. Add Particles to Photoshop Document
Once you’ve created a new layer, grab the Brush tool (B) and right click and choose to “replace brushes” and load that new brush set that you downloaded from Brusheezy.com. With white as your foreground color, click a few times in the center of the document to create a randomized white pattern.
3. Add Mosaic Filter Effect
Go Filter>Pixelate>Mosaic and set the mosaic option to something that looks good to you. I used 25px (this will all depend on the size of your Photoshop document that you’re applying this effect into.)
4. Choose Blend Mode to Blend
My plan is to duplicate this texture pattern and use blend modes to create an effect which will interact and change depending on the background image behind the graphic. In this case I used a combo of Soft Light and Overlay.
5. Use Hue and Saturation to Add Color
If you duplicate your mosaic layer, you can colorize one of the layers with something like Hue and Saturation. Here I used Hue and Saturation set to Hue: 50, Saturation: 100, Lightness: -40. You can push or pull and adjust these to your liking depending on what photo or background you’re using behind your misty mosaic effect.