I searcheed the web for the cumulus plug in, but it's nowhere to be found anymore, maybe you could contact Flaming Pear and see if they can do something for you. My copy came on a freebie CD from an old Computer arts issue. But you can use Terragen to do it, it's free for non commercial use, and it can produce decent enough clouds to use in Vue. If you need a tutorial on how to do this in terragen, let me know.