Atheists who suicide thinking there's no afterlife would likely end up just as they expect. Their consciouness probably implodes into a sort of black hole of vegetative nothingfullness, possibly forming a quantum pocket of "signature" energy. THis quantum energy (the remnants of the atheists's disembodied and tortured mind and emotions) might then attract and conglomerate with other quantum pockets vibrating at the same low level.   Like droplets of dirty oil on the surface of a pristine pool of eternal consciousness.

What this might feel like is anyone's guess. So if you're the type that needs everything planned out and accounted for in advance, I suggest you're better off where you are right now. Especially if you're over 35 - do you really want to take the chance of Smelling Like Teen Spirit forever?