Hi all
And why not a model of architecture ?
All is free !
1 Choose your 3D Model
2 Load this free program for Mac or Pc(Button loading is on bottom page)
3 Load your model and re-Save it as Dxf file or save the screen as an image !
4 Import in Zbrush as a dxf file or as an image !
Have fun building 
Pilou