The Liquib Mosaic Tool was applied to a photo of book shelves in a book store.  Tile Shape was set to Octagonal, Tile Content to Averaged Colors, Tile Size to 22 and Shape Regularity % to 22%.  The low Shape Regularity % gives the rendering process flexiblity with adjusting the tile shapes to align with image edges, though the resulting tiles don't much resemble ideal octagonals.