Perhaps like me, you have learned the hard way
that an 8-sided shape won't tessellate.
Octagons need other pieces to cover the surface.
Above a traditional quilt pattern with octagons plus diamonds...
Octagons and squares.
Squares fill the gaps well.
Squares and long hexagons.
Once we get above six sides we are into shapes that do not tessellate.
No charm quilts below.
5 = Pentagon
6 = Hexagon
7 = Heptagon
8 = Octagon
9 = Nonagon
10 = Decagon
We have added to our vocabulary if not
our repertoire for tessellating charm quilts.
Pentagon and Heptagon
These complex shapes, however, do make interesting pattern when combined with other shapes. You rarely see them in antique quilts but there are lots of ideas on the web for pattern with Nonagons and Heptagons, etc.
A ring of heptagons
A paper-pieced decagon.
Buy the pattern from Endulzar's Etsy Shop
Long hexagons---6 sided shapes
(You may have noticed I have skipped the 6-sided shapes---hexagons---in discussing pattern that will tessellate or cover a surface with one piece. That's because it is such an ENORMOUS category. I am still working on sorting it all out. )