the ones i made were
the Scrapped Smasher, and
the Busted Blade
so if anyone sees them in-game it'd be nice if you mentioned it here, because i'd love to see they made it.
How do I make items for the game?
go here:
http://www.reddit.com/r/TroveCreations/read a few of the most important looking wooden signs next to messages, the rules can and will change around as the devs want different things, so learn whatever you can. also, search up whatever idea you have now, to make sure it hasn't already been made.
as for voxel editors that you could use:
Qubicle appears to be what the Trove developers use, but it will cost quite a bit of money to be able to export (aka submit as a design).
Zoxel was what most people were using when i entered.
MagicaVoxel is what i used, i think it's pretty good.