So what did I learn?
Expand the bottom layer
In the original card, I cut up the image and put half on top and half on the bottom. I didn't take into account of how the thickness of the acrylic would make it impossible to see the images line up. It still looked cool so I mailed it, but I wanted a more complete look to it.
Use a visual cue
With 24 square inches of space to use, I was only using a small fraction of them. With an expanded bottom layer it would help to have a visual cue to let the user know where to hold the card to see the images line up. I started with circles, but spirals look cooler.
Use complementary images
With the visual cues of the spiral, I needed to make sure that I had two complementary images. This means that two shapes had to come together to form a solid mass.
So with all that in mind and the results right below this, this Instructable is meant to show how the layers were created in Illustrator. Several other imaging programs can be used as well. I am just using what I'm used to.
Materials and Tools
Scrap 3/8" acrylic from Tap Plastics.
Laser cutting and etching with Squid Labs' Epilog Mini 24.
Vector illustration with Adobe Illustrator CS.
Step 1: Make a Spiral
I punched in:
Radius = 4 in.
Decay = 90%
Segments = 100