The Blender file contains the 1K specular and bump maps from: http://planetpixelemporium.com/earth.html
- Go to the Modifier stack of the icosphere.
- Adjust the subdivisions of the 1st modifier to change the resolution.
- Adjust the strength of the 2nd modifier (negative) to change the land & ice displacement above the oceans.
- Adjust the strength of the 3rd modifier to change the topographic displacement on land.
- Export the model as an STL. Enable the "Import-Export: STL format" addon in the user preferences if STL doesn't show up in the "Export" menu.
To wrap your own displacement map on a sphere, it needs a UV map. Select the sphere. Go to mesh edit mode (Tab). Change the view to "Front" (numpad 1). Select Mesh -> UV Unwrap -> Sphere Projection. In the displacement modifier, set the "Texture Coordinate" to "UV".
I didn't intend to print this model by itself. I used it in another project.