You can construct any region you need, read up the docs I referenced in my 1st post. There are many many ways to do this. Generally see ImplicitRegion for custom regions. There is also data. For example some SolidData:
SolidData[]
RegionPlot3D[tmp[1], PlotPoints -> 50, Boxed -> False]
Or PolyhedronData:
With[{r = 1}, RegionPlot3D[
PolyhedronData["Cuboctahedron", "RegionFunction"][x, y, z], {x, -r, r}, {y, -r, r}, {z, -r, r},
Boxed -> False, Axes -> False, PlotPoints -> 50, Mesh -> None]]