Turn any photo into a dot grid artwork with these Photoshop actions. You'll get great results with dots that change size. They get larger in brighter areas and smaller in darker areas. Free download available.
Blend Mode: Soft Light | Opacity: 25%
Create another group and this time name it 'symbols'
Before anything else, to make this work easier and more organized-looking, we need Rulers and Grids. These can be accessed by simply going to View > Rulers and View > Show > Grids. Here are my setting for both the Rulers and Grids (this can be accessed by going to Edit>Preference):
Now that we have that, we need to add giudes and this can be done by simply clicking and dragging from the ruler. Click and Drag from the vertical ruler if you want a vertical giude and vice versa. Here is how I divided the canvas (each icon being 50x50 pixels big and a 25 pixels space between each one):