What state are you in? There are quite a few where clawed frogs are illegal. Definitely a fun pet to keep though. I would only keep a male in that size though, females get quite large. Dwarf frogs are another option, though much smaller.
I’d pass on chameleons, very difficult to keep them.
I’ve heard Pac-Man frogs can go in that size.
Scorpion or tarantula would be fun (or a wennerae mantis shrimp if you want to fill it with saltwater).
One or two dart frogs would look nice (and you could trick people into thinking they are toxic, but captive ones are not).
Small Skinks could work but otherwise not many lizards that come to mind. Sources always say anoles can go in that size, but IME there is a huge difference in behavior between a small and large cage.