Well, you might think they're not but...
Best "decor" for a tree frog? I had a stick, like a legit stick from a tree( I'm forced to be a cheapskate right now.) in his tank and one of those wood log tunnel things. I also had some rocks from outside. Since he got sick, I chucked everything that could possibly have mold on it. He's left with a round rock, his water bowl and this goofy looking $3 plant I got at petco that sticks on the wall of his tank. With a suction cup! Can he actually CLIMB that? O.o
Also, best, and cheapest substrate for a frog? I've honestly had a frog for five years and tonight was the first time I even LOOKED at substrate. O.o Granted, he's a gray and they've got a high tolerance for dryness, like a toad. But I'm just looking at the glass floor of that tank going, "He's getting old, he deserves new squishy flooring!"