Step 2 :Open a new image 30 pixels x 30 pixels and zoom in so you can see to work on it : depending on your screen size and resolution, this could be as much as 1000% or even more. Set your paintbrush tool to shape square, size 15 pixels, step , hardness, density, thickness and opacity all 100 and rotation 0 on the Tool Options palette (click F4 if it isn't visible.) Place 4 "dots" with your 15 pixel square brush - one in each corner of the square, with the darkest colour top left, lightest bottom right and mid colour in the other two corners (screen grab #1.) Save this image as a plain gingham tile.

Step 3 : If you would like the gingham squares tobe decorated, with the effect of simple embroidery, set your paintbrush size to 1 pixel (leave all other settings unchanged) and draw simple designs (hearts, flowers, stars etc.) in the contrasting colours on each square, pixel by pixel (screen grab #2) You can decorate one corner, diagonally opposite corners, or all four. When you are happy with your design, save this tile too, under a different file name.

Screen grab #3 shows some more ideas for simple designs suitable for a 15 pixel square.

            
Screen grab #1                    Screen grab #2                                 Screen grab #3