This is a Christmas ornament I designed last year for friends and family. They were a big hit so I wanted to share it here. You can place four different pictures as lithophanes, and change the titles to personalize.
I printed it in woodfill PLA to make it look like a ginger bread house. Print a blank one and decorate it however you like!
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Parts List

2X – Single AAA battery holder – Amazon Link
1X – Small slide switch – Amazon Link
1X – Small LED flashlight like one of these: Walmart Link Amazon Link

• You can buy these at Walmart (camping section) for $1.

1X - Small eye hook
2X – AAA battery
3X - Small screw, for switch and battery cover (optional)

3D Printed Parts List

1X – Battery-LED Box
1X – Top
1X – Front Panel
1X – Back Panel
2X – Side Panel
4X – Side Trim
1X – Battery Cover
4X – Lithophane (47mm X 47mm)
2X – Holly Leaves
2X – Holly Berries

Lithophane Prints

Each lithophane should be 47mm X 47mm square. There are many methods for generating lithophanes. Slicers like Cura have built in options for generating a lithophane from a picture.
General rule of thumb for lithophanes is to pick an image with a lot of contrast. Simple images will turn out better. Either way, experiment and see what looks best.

LED and Battery Pack

The LED board needs to be removed from the flashlight. See build guide below.

Assembly

Check the fit of the four side panels to make sure everything seats properly and there are no gaps. Since these need to be printed with supports, you may need to do a bit of sanding and cleanup. See below for build guide.

Customizers

You can customize the text on the top using the customizer link on this page. Customizers for the other parts can be found here:
Front/Back Panel
Side Panel