These are wood engravings of actual old figureheads, from various ships.
Wood engraving is an antique process of engraving an image on a small block of end grain boxwood (traditionally; now I use a resin substitute, as engraving blocks aren't available). When the block is inked, wherever the surface is left it prints, and the white lines are where the block has been engraved into. It is a rare skill now, although this was the main way illustrations were done for books, newspapers, etc. in the late nineteenth century.