Research has shown that any picture in which the subject is looking directly ahead will have eyes that appear to look at you no matter the angle from which it is viewed. This is because pictures are 2D representations of a 3D world. As such, our brains ignore the clues that remind it that we are looking at a flat object and focus instead on the dimensional illusion created by the representation of light in the picture. No matter the angle from which we see it, even if it is a very skewed view from the side, we'll perceive it as a cohesive picture oriented toward us.
The alteration I'm describing adds an actual 3D effect to the picture which is not consistent with the cohesive view, making it disturbing and, thus, creepier than a static picture with eyes that look directly forward. It works by receding the eyes below the surface of the picture. The depth of the eyes allows the edges of the eye sockets (which are not receded) to hide the whites on the side it is being viewed from, just as would happen if an actual person was turning their eyes toward you.
Step 1: Gathering the Stuff
a graphic file of your picture of a subject looking straight ahead
OR two prints of the same subject that are the same size and resolution
poster board or card stock
a sharp craft knife
markers or colored pencils
frame with or without mat - the effect is easier to see without the frame's glass
Step 2: Printing
For this I'm making a picture for an 8"X10" opening so I am printing the image on a single sheet of standard cardstock.*
Using graphics software, format your picture to fit the page. Save your document. Then save the document again with a new name. On the second picture, crop everything but a box around the eyes. This box should extends about 1/4" or more around the eyes in the exact same spot on the page. You can simply use a second copy of the picture, but I only like to print the eyes to prevent wasted ink.
*A larger picture can be assembled from tiled standard prints--as you might do using your home printer. This is purely a matter of your own choice. However, it is important that each eyes be completely on a page and not divided between two sheets where the edges of pages might connect, however the picture is printed.
Step 3: Removing the Eyes
Step 4: Blending
Step 5: Creating Blank Layers
Stack the three pages with the eyes on the bottom, the blank in the middle, and the full picture on the top. Compress them down and look at it from either side to see if you are satisfied with the depth of the eyes. The deeper the bottom layer of eyes are below the original picture, the stronger the eye-following effect. You can cut more blank pages of cardstock to make the eyes recede more. However, going too deep begins to look absurd. I like two layers of blanks on a small picture like this. A larger picture allows for more depth and a very small picture should only have one blank layer..
Step 6: Assembly
Apply glue to the top of the eye page everywhere but the eyes. Line up the blank page(s) so the cut box is over the eyes and press it down. Again, you may want to place a few heavy books on top to keep the pages flat while the glue dries.
Apply glue to the back of the photo page. Arrange this over the other pages so the eyes are lined-up and press together. Place books over the stack to hold it tight while the glue dries.
Once the glue is dry, frame your picture.