I wanted a simple frame-like lamp that can be used to display lithophane art.

TL;DR

Requirements for the Lithophane plate:

• Must be of size: 140x105mm, with rounded corners of size 5mm.

• Must include a rounded edge/lip of 3mm width and 2mm thickness. For this purpose, the attached NegativeMask.stl can be used as a negative volume within your slicer of choice to adapt lithophane plates created using online generators.

Requirements for the electronics:

• See Figure below for the dimensions of the switch and USB-C port.

• LED strips of thickness up to 8mm can be used, though 5mm wide strips are recommended.

• Required length of the LED strip is 460mm.

Features

The design includes the following features:

1. Support of both portrait and landscape lithophane plates (the different designs are included in respectively named directories).

2. USB-C port with power switch.

3. 15° tilt view angle.

4. No supports required for the print.

5. No glue/screws or similar required for the assembly.

Assembly

In order to assemble the frame, you will need a USB-C port and a two-pin rounded switch. I do not have exact model numbers but the dimentions of the  components I used are shown in the Figure below. I think you will be reasonably safe ordering any components that "vaguely" look similar and have the same dimensions as shown in the Figure below:

The middle frame has an inner thickness of 8.8mm meaning strips up to 8mm in width could be used, I have however only used 5mm wide strips in my assemblies. the total length of LED strip required is: 460mm.
The electrical assembly is quite forward and is shown below:

When assembling the electrical components, I recommend doing it in the following order:

1. Deposite some solder on the switch's poles.

2. Cut the USB's red cable to leave about 30mm of wire attached to the port. Keep the free piece of wire aside, as it will be used to connect the switch to the LED strip.

3. Insert the switch and port into the USBSwitchSupport piece.

4. Solder the red wire from the USB port into the switch.

5. Solder one of the ends of the free piece of wire from Step 2 to the switch.

6. Insert the USBSwitchSupport piece into the BackPlate. You will need to apply some pressure as the two pieces are simply press-mounted into each other.  

7. You will need 460mm of LED strip to cover the inner circumference of the BackPlate.

8. Solder the free end of the red wire coming from the switch into the LED strip's 5V and the black wire coming from the USB-C port into the the strip's GND.

9. Stick the LED strip to the inside of the back plate. I recommend gradually removing the protective film from the strip rather than doing it at once.

With the electronics mounted into the BackPlate, all that remains is to push the lithophane plate into the MiddleFrame, push the BackPlate into the MiddleFrame and secure the assembly using  RightFoot and LeftFoot.

Adapting Lithophane plates to work with the design

The dimensions to use when using online generators (such as https://itslitho.com/) to create your lithophane plate are:

• Height and Width of 140x105mm, with rounded corners of size 5mm.

• Border of width 3mm and thickness: 2mm.

Most generators I found online do not allow to create rounded rectangles, or rounded borders. For this reason you can use the attached NegativeMask.stl  as a negative volume, and add it to the generated lithophane plate within your slicer. The GIF below shows what that looks like within the prusa slicer.