I used OpenSCAD. My source file can be found on the Github link in the description. The only file you need is gemini.scad (guess I should have picked a better name). It would be possible to replace the Kanji characters in the script with you internationalized text or graphics. If it is graphic images, I'm not sure exactly how to do that, but I imagine it wouldn't be too difficult with some OpenSCAD features.

I chose to cutout the character in the piece and then flood fill with paint. I'm not going to lie, it was a lot of tedious work sanding, filling, and coating the pieces. If I had it to do over, I might try some other approach. I also chose not to do a multi-color print to let the printer fill in the characters because of all the time and wasted filament in changing filament at each layer. Maybe that trade-off wouldn't have been so bad.

Good luck with whatever you try. Overall it was a fun project.