I think that most of the users of Powder Toy would love to see a way to trick gravity. I'm one of those. I am organizing this post to increase the chances, thing that many people didn't, and could be the key.
This will be kind of long, so i made a summary on the end.

Gravity: what is it, first of all?
Gravity is what pulls objects to the center of the Earth, or as we usually say: pulls the objects down. It is also what keeps the Moon spinning around the Earth and the Earth spinning around the Sun.
So, it pulls stuff down. But how is it used on Powder Toy?
On real life, gravity is complex. Basically its created by the core of the Earth wich is basically melted iron and nickel at over 3.000ºc (i think) wich creates a really strong magnetic force. That magnetic force is so strong that it doesn't only pull metal: it pulls any kind of matter. On powder toy, obviously, it isn't that. It's a script that pulls the particles "down".
But how will we change it's force?
I may not be a scripts expert, but i am sure that there is a way to change the intensity of the gravity. By decreating or increasing it's power we could make lots of stuff! We could have a gravity as low as the Moon's, normal as the Earth's, big as the Jupiter's or even HUGE as the Sun's. Or we could have absolute no gravity. It's up to you.

Summary
Basically, a way to change the gravity on Powder Toy is messing with the scripts. By increasing or decreasing the intensity of the gravity on the scripts you can change gravity. By doing this we could have the gravity we want. I wish I could make the programming myself but I'm eleven years old and I still have a lot to learn. Thanks for reading and I hope that a gravity edition menu would appear on a future version of Powder Toy. If the moderators have any kind of question ask me and i will do my best to awssner it.