Right-click on the Background layer then choose Blending Options. Enable the Bevel & Emboss option then set the Technique to Chisel Hard and Size to 1-2px (so that it looks similar to the image below). If the bevel looks too strong, you can lower the Highlight/Shadow Opacity setting on the bottom. Click OK to apply the layer styles.
Now we need to turn this image into a pattern. Go to Edit > Define Pattern. Name it anything then click OK.
Close the current document without saving and switch back to your main Photoshop document. Create a new Pattern adjustment layer by clicking on the New Adjustment Layer button in your Layers panel then selecting Pattern.
Select the brick pattern then click OK.
Change the blending mode of your layer to Linear Light. You’ll now have a brick image and this is what your photo will look like if bricks came in every color and shade.
Because bricks don’t come in every color and shade, we need to compress it to a more limited color palette. We’ll do this with two layers; one to affect the tone and the other for the color. In your Layers panel, click on the New Adjustment Layer button then select Posterize. Move this layer below your Pattern Fill layer then change the blending mode to Luminosity. The Luminosity blend mode prevents your layer from affecting the colors in your image.
Adjust the Levels setting to anywhere from 4-8.
Now we need to compress the saturation of the colors to a more limited range. To do this, create a new red Solid Color fill layer by clicking on the New Adjustment Layer button in your Layers panel and selecting Solid Color.
Pick any color then set the S (Saturation) to 75% and B (Brightness) to 100%. The H (Hue) can be any color. Click OK.
Move this layer below your Pattern fill layer then set the layer blending mode to Saturation.
Here’s the final results! You can adjust the opacity of your Posterize layer if you need to bring back more tone into the image.
If you want your brick photo to look more like the official Lego Photo app, simply change the blending mode of your Posterize layer to Normal.