Open the image you want to edit in photoshop. You can size it to whatever you’d like, even if it gets a little pixely, or has artifacts.

Next, apply the filter at Filter > Pixelate > Mosaic. The cell size is your choice. Experiment with different sizes if you’d like. Since I like all the different color detail in my picture, I made it relatively small. Important Note: Remember what size you make it!

Now create a new document, with the height and width of your mosiac cells. (Mine is 9 pixels) Make a circle selection like the one below:

Press Control-Shift-I to inverse your selection. Fill this with white (or black, white works better though) Now it will look like this. My background layer is lime to show the shape. Hide the background layer and any other layer except the white corners. Select only the layer with the white corners and transparent(not lime, because thats hidden) circle, and go to Edit > Define Pattern. Name it Dots.

Go back to your other image. Make a new layer on top, fill it with any color and apply these blending options:

In the general blending options:

In the Pattern Section:

Now your mosaic is done.

Here is the same one with a bigger pixel size, and black pattern, using all the same steps.

Some Pattern Examples:

These are all PNGs so you can save them and use them. The first two are 20×20 and the last two are 30×30.
   

Keywords: Adobe photoshop tutorial, circles, patterns, orbs, halftone, photo manipulation, cool photo shop tutorial, lips, illusion.