I am thinking the best way to do it, and get it thick enough to be useful, would be to use a concrete sprayer (often known as 'shotcrete').

Here is some info on the process (for concrete):  http://www.toolbase.org/Technology-Inve … rete-walls

But, since I have never heard of it being done with papier mache, I suspect you would have to buy your own spraying machine, unless you found someone who was interested enough to loan you his machine, with possibly unpredictable (and damaging) results.

If I were you, I would mix up a batch of papier mache, and attempt to stick it to concrete manually.  It may not work, or you may have to experiment with different types of adhesives.

I, too, would love to hear what you come up with!

Sue

There is a yahoo group devoted to all kinds of uses of "papercrete", which is what I think might be of most benefit to you.  There is TONS of information on how use this mixture for building blocks to sprayed on insulation

HTH

If you have any level of humidity, you might be in trouble because papier mache is very hygroscopic unless thoroughtly sealed.   Also laying it in any thickness in one go will take aeons to dry.
To stick to the ceiling, I would guess that a wash over a limited area with PVA before trowelling a thin coat of PM onto it, ought to hold well.   When that is dry you could trowel another thin coat, and so build it up to the level you want.
I love DIY projects.  Well done.
DavidO