Heartwire
Awesomesauce
Yeah new towers are the ones you create.I just played "new towers". Not created by myself, not by friends either though.
I'd give it maybe 1 or 2 more goes and see if it unlocks.
It could be delayed (like buggy).
But AFAIK, everyone who has tried this unlocked the skin.
Of course you have to complete every tower but I'm sure you're doing that already.