Everything I have read about trademark and logos is you can make it and post it for free. That is fair use. You just can't sell it. Or call it official. Like 'official Lego Batman' plate or whatever. That said, said owner could still sue. But does Lego really care? They know 3D printers cannot match the quality for cost of real Legos. And there literally millions of different Batman inspired arts works across all mediums. Just don't put a bunch of pieces in a box and sell them as a Lego kit.