Bear in mind that polka dot plant needs bright but indirect light, so may grow towards light and ruin your display if it's too dark where you've positioned your terrarium.
There are many varieties of polka dot plant, with leaves in shades of pink, purple, red, or white and green. They thrive in warmth and humidity, and are compact and slow growing, making them another perfect choice for a closed terrarium. Bear in mind that polka dot plant needs bright but indirect light, so may grow towards light and ruin your display if it's too dark where you've positioned your terrarium.