Hi Felix,
my example didnt take any time at all, dont worry... The point of my example was basically showing the result with only "2d curves"...

The last 2 pictures you showed would be done easy with MoI alone as solids....This would be your best bet.. The previous ones, that showed leaves and things more like "Vines" or branches and stuff, could be acheived with the 2d geometry and BobArt... Good luck.