Not a lot of people have done it that way, mainly because they don't know that it can be done. But yeah, I know several who have done it. If I had thought about it when I did mine, I'd have had spray-on insulation done. It'll save 3 or 4 days of insulating, and it'll cost the same or less, all things considered.
You'd want to use foam boards in the larger voids, like the ceiling and walls, prior to spraying. One-inch board should work well. Use Liquid Nails and/or spray adhesive to secure the foam boards. This will reduce the amount of spray-on foam needed, and foam boards for the larger voids will provide the same insulation as the spray-on insulation will.
Be careful about spraying the doors, because the foam will expand and may really screw up the lock and window mechanisms. The foam installer will know where not to spray. I didn't insulate my driver and passenger doors at all because of the windows, and a well-insulated passenger or driver door will be a significant problem if the electronic window motor or even a window needs replacing.
Once the spray-on foam has cured, it can be sanded or sliced down to a smooth-ish finish and then can be covered with either the panels that came with the van (if any) or silver Reflectix (lets you know what Jiffy Pop popcorn feels like), or whatever you like. Some never even bother covering it up.