Create new file with size 160x120 pixels. Fill it with solid color (say, blue).
Apply noise filter (Filter menu - Noise - Add Noise). Try different amuont values to choose what you like most.
Now we need to resize our image (Image menu - Image size). First, change pixels to percent in width dropdown. You will notice Width value is now 100 (per cent). Change it to 1000 (we want 10x zoom, which is 1000 per cent). Now, most importantly, goto resample image dropdown and set it to nearest neighbour! This will give us nice squares with hard (not antialiased) edges.
Cool! Now we already have a nice pattern built from mini squares (each is 10x10 pixels). But we can do more.
We will need a 1-pixel gap between the squares. To do so, we will need another image to help us. Create new image, 10x10 pixels, transparent background.
Use pencil tool to draw the lines on the left and bottom edges of the image (or right and top, nevermind). After that, select all (Ctrl-A) and define a pattern from selection (Edit menu - Define Pattern). Then, you can close this temporary image and return to our main image.
Create new layer and fill it with the pattern we just created. To do so, open Fill dialog (Edi menu - Fill), choose Pattern, and then in the list of custom patterns, find the one we need (last one).
oh yes! now we have blue squares in layer 1 and a black grid in layer 2. This is not all yet!
Hold Ctrl and click layer 2". The black grid should become selection. Then
Then, simply hit Del button, and you will get the 1-pixel gap between the squares. Why would you need it? Read on!
Now that each square is separated with a pixel of transparency, we can apply layer effects. I used Bevel and Emboss, you can other. Note the values shown in the screenshot: size is 0, shadow mode - color dodge with opacity about 50%. When applying layer effects, always remember than no effects looks better than too many effects. So, be careful when setting the values.
To make our iage even better, how about a slight overlay of the gradient? Note the values: gradient - black to white, style - radial, blend mode - overlay.