Well, the thing is, copyright, depending on country, lasts a different amount of time after the death of the author/artist/creator of the work.
I believe at present, in the US, it is 75 years after death. Different nations have different ways of doing it.
However...
You may want to contact the fellow at this site, since he has made models of MC Ecsher's work, some 3d Computer-based, (admittedly a long time ago), and a number of physical models.
http://www.gamedecor.com/abasworld/He might have some handy-dandy tips for you. =)
Tell him KE/Kaelis sent you. =)