Lots of symmetrical boxes with any number of sides. Parametrical, easy to use OpenSCAD file for n-sided boxes with lids. The lids have an inner lip/flange. See pics for the sizes I have tested, printed in red PLA. For n<=2 you'll need a custom space-time continuum!

Either use the STLs directly or change the parameters in the simple OpenSCAD file to get any custom shape and size. The STLs contain both box and lid, use the .scad if you only want one. If you print these with concentric infill on the outer layers then the pattern will repeat itself for pretty accentuation of the geometry. Maybe you can see this on the close up lid pic? For completeness I also included a round box which actually has 99 sides.