I would do it with MoGraph. Here's how:
1. map your texture onto the sphere (in material's luminance channel);
2. create a cloner with a small cube (converted to geometry) as the cloned object and set the cloner to object mode (targeting the sphere) and the method to surface;
3. for now, turn on render instances in the cloner (speeds things up);
4. create a shader effector, turn off the default scale parameter, and turn on the visibility parameter;
5. in the shading tab, set the channel to luminance;
6. now turn up the clone count to a very high number and hope that you don't run out of ram. :)
7. when you get the clone density you need, turn off the render instance box in the cloner and hope you don't run out of ram.
8. if all went well, make the cloner editable, select all the clones, and run the connect + delete command. That will create a single object from all your clones that can then be exported.
Example:
4085_citylights.zip
