The best replacement for polygons is nurbs.

The best alternatives to polygons are rated as following:
★★★★★  nurbs
★★★  non polygons
★★  regular polygons
★★  triangles
★  pixels
★  sprites
★  quadrilaterals
★  nonpolygons
★  irregular polygons
★  voxels
★  atoms
★  solid figures
★  histograms
  not polygons
  shapes

Your alternative for polygons is not listed? Suggest!
Speaking about polygons, one probably shouldn't forget about tessellations.

Other search terms related to polygons and their ratings are:
★★★★★ tessellations
You have in mind a companion for polygons and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of polygons in all years. Click on graph for more.
polygons
nurbs
non polygons