Nexus, you've got an interesting theory.
For myself...well, claiming to 'know' would be arrogance, I think, and everyone experiences the world in their own way, but my own belief is that our personal, individual consciousness, which is part of the universal Consciousness (only, being separate physical beings, we often fail to realize this), becomes, after death, fully aware of that unity. If it wants to.
I think there's a lot of sense in the accounts of the Bardo Thodol, the Tibetan Book of the Dead; most of your 'afterlife' experiences are illusory, based on your consciousness at the time, but you can, if you really want to, go beyond that and reach union with the ultimate Reality. Which would - to go by people who've experienced it in this lifetime - be beyond words, but...pretty amazing. Probably the origin of the very watered-down concept the religions have called 'heaven'. The hells are illusory and temporary; ultimate Reality is bliss. Tallies with what I believe about the idea of hell, which is that it's our old primate ego thing about wanting people who don't agree with us to suffer, projected out onto the Universe as if the Universe somehow also 'wanted' what we (or the people of our little group) want. Bizarre!
Going back to the question, what do I think atheists experience after death? Whatever they need or want to experience. That may be nothing at all, if they're truly atheist (and good luck to 'em, if they're OK with non-existence, some of them have been among the most moral people I've met and I have no grudge against them whatever), or they may have some hope of an afterlife hidden away in their subconscious, in which case that's what they'll get. What anyone else, or anyone else's God thinks of that, is frankly none of their business. 
_________________
"Grunge? Isn't that some gross shade of greenish orange?"