8192 pixel wide elevation map used on planet of Earth's radius would have resolution of around 5km. While the procedural algorithms would refine it down to centimeters anyway, it won't look like Earth or like anything much actually, because the existing algorithms are tuned for features below 100 meters, and can't generate erosion patterns and terrain details that are missing from your coarse map.
Also, even the base map that looks good in 2D relief usually needs to be corrected for 3D, once you see it. Generating elevation data that look good in 3D is quite laborious process, and right now there are no helpers in OT that would simplify it.