Well, in brief... there was a ruling in the US that concept art, whilst copyrighted for its medium, did not, by default, mean that it was copyright for all other mediums, particularly if the concept art only existed in the one medium.
Please bear in mind that this is a judges ruling and thus subject to any future ruling that may be of a different stance, however what it essentially means is that if you produce concept art then you are protected if other people copy/use that concept art in that medium, or in a related medium... so digital art would be protected for any copied drawings, digital 2d images and so forth...
However nothing says that it would mean that the deisgn within that art was copyrighted for production in another medium: so if you took the concept and produced a 3d model from the 2d image, then, under certain circumstances, that would not be a breach of IPR... particularly if the owners of the 2D art did not have any competitive product or *item* in that 3D medium.
So by showing 2d art, another party *might be able to* copy it into a 3d medium and sell that 3d medium item without infringing copyright.
Until the issue is resolved at a higher court or with additional cases, its now prudent to withhold concept art until you are ready to also produce it in the 3d medium i.e. as a physical product...otherwise a possibility exists that others could use it without infringement by *beating you to market* with their own version of it.
Now we can protect our Designs™ under UK Law, that also covers us in the EU, but not under any other jurisdictions... especially the US where this judgement took place.
Thus, until it is resolved *unequivocally* we're going to have to be more careful in what images we release of 2d concept art or WIPs of models... especially given that our development time frame is quite lengthy.
It may all come to nothing, and be a lot of smoke with no fire.... but we've been advised to be more cautious. /em shrugs
TLDR: a judge made a weird ruling thats gotten everybodys knickers in a twist.