Not very much, I have that tank.
I think clown frogs stay small or green tree frogs.
I would like to know, Because i wanted to convert the tank after my crestie goes.
As for lizards the smallest I can think of are anoles but I think it would still be too small.
Yeah I never truly understood why companies make tanks so small, when there is nothing really in the pet trade that would fit in there nicely. Anoles are not an option, many people are misinformed about their care, they should have a minimum in my opinion a 20 tall. I would say your best bet is a green treefrog, or some type of reed frog which also stay relatively small. As for a lizard, there really is nothing that would work in there.
I have a phelsuma klemmeri in a 12 x 12 x 12 and have had her for about 2 years. She's only about 3" long. She's in a planted tank with horizontal bamboo. I'll post a picture when I get back home to my other computer where the pictures are. The breeder who sold her to me told me this size would be fine and it is. The only thing is, if you get a young one, you have to gecko proof it because they can squeeze out of anything. The day I got her I couldn't see her in the tank and my son later found her on the floor behind the bookshelf. And this was after I had gecko proofed it. Now she comes out whenever I mist the tank and will lick nectar from my finger, but she really isn't handleable. Julie from gecko ranch may have more info.
Tree frogs or Reed frogs would probably be your best bet. You may be able to get away with a Petri's Gecko or Dune gecko. There are a few other gecko species that would do ok in that size enclosure, but you would really have to gecko proof it. Lygodactylus or Tropiocolotes would do nice but would probably be out and running within 2 minutes.:main_laugh:
No, I thought about putting a posion too but only one could really fit and be happy.
So one I think would be fine but not a pair. 10 gallons are usually the size minimal requirements.
I'm not an expert on this but I would say any type of tarantula or scorpion really, just browsing through things I see most people keep them in kritter keepers so that's why I think they would be fine in your tank.