Bring your favorite images to life by creating a lithophane model and 3D printing it. When illuminated from behind, the details in the photos are revealed.
thus giving you a good contrasting lithophane. Make sure you do not increase this value too much; otherwise, you can expect overhangs in the STL model, and you'll need to use supports, which will ruin the lithophane
PLA is one of the cheapest and most used FFF materials. It is possible to find transparent PLA and in fact, when it first came onto the market, most PLA was transparent. However, it is difficult to get clear prints with PLA, and the other materials mentioned are normally a better option...