I removed the stickers and filled it with black aquarium gravel.
I chose to plant a few different anubias varieties. I got these plants online several months ago, and they're holding up to my abuse quite well. I'm not so good with most aquatic plants, since I'm always uprooting and rearranging them!
I arranged them how I wanted in the planter.
Then I carefully lowered the planter into the tank, and viola!
I love how it turned out. It adds some more visual interest to the tank while still being easy to maintain, and it doesn't create a hazard for the fish.