#18 - I do like the lizard concept. I think though that the Aboriginal dots make it a little complicated. When the logo is displayed large it is certainly easy to see, but when shrunk (ie, as a watermark on images) the dots all blend in and make the symbol hard to recognise.
I much prefer the shape of the lizard that you used in #18.
What about if you keep the #18 shaped lizard, but made it a solid shape, maybe a nice lizard green in colour that isn't too dark that it blends in with the background.
Also, I think if you made the text a little larger in relation to the logo that would look a little better too.