It uses the tiles from their online satellite map, and can output images in increments of 1x1, 2x2, 4x4, 16x16 tiles (each tile being 550px by 550px). Here is an example with 2x2 
If you have any suggestions or bugfixes, feel free to fork or comment.
EDIT: Also works for a single tile, also clarity.
Cloud height is at about 60,000 feet maximum (in the tropics http://www.srh.noaa.gov/jetstream/clouds/height_max.htm). Let's be generous and say this is 20 km maximum height.
Earth's diameter is 12742 km. The clouds are about 0.15 % of this size, relatively speaking. The full images are about 11k by 11k, so we can say that 1 px is roughly 1 km. This means that the clouds will be on the scale of 20 pixels, roughly.
You know what, this might actually work.