For atheists: Is there any chance that there are aspects of reality that we can't perceive?

Absolutely.

The world around us is so much greater than our own ability to know it completely - to say otherwise is to betray your own arrogance.

Always. In fact, there are quite a few aspects to reality we choose to ignore. Otherwise we would suffer from constant attempts to process everything we observe. The trick is to sort out with your amygadala the really relevant bits. For example, I regularly have no experience of a living god, thus gods are not really relevant. Not that I'm not open to the idea of gods if they ever happen to make a difference, but the fact is they don't. People, however, do make a difference, so if the Spanish Inquisition stops by I might pretend believe in god. Please ask them to bring the comfy chair though if that's going to happen. Right nice of them...

Sure. But if it cannot be perceived in any way, there is absolutely no reason to suspect anything specific. Right now I can't see under my bed, but that is no reason to postulate a monster is under there.

The blind analogy is not that good, as there are a whole lot of wavelengths none of us can see that have been very well described with other means.

I think the answer is no. I think all aspects of reality can theoretically be perceived in some way. I'm taking a very broad definition of 'perceive' to include all possible indirect scientific evidence, not a limited view to just human senses.

Not an atheist, but I can't resist: theoretical physicists are speculating that 93% of the universe has to be made up of dark matter and dark energy, which is making it expand. There's no proof for it other than numbers crunched on a blackboard, but the stuff has to be there, or a lot of things in our Cosmos that are happening shouldn't be happening. So far, no proof for either dark matter or dark energy, yet I'll bet a lot of atheist scientists readily accept it.

Yes, a 100% chance. There are colors we can't see (infrared) and sound frequencies we can't hear. Some of us have genetic disposition to taste Kale differently. Odds are that we are not biologically built to understand the absolute truth of the universe. What are the odds that we evolved on our singular environment with the capability to understand everything?

There may very well be.

By the way, explaining color to a blind man is not a difficult as one may imagine.

Yes but you have to be able to prove it. If you can't prove it, any religion could make up anything out of thin air and then use it to justify their political agenda. Have you ever noticed that different religions have different realms of your unperceivable reality? They are often in contradiction with one another.

yes. in fact, there is evidence that the brain may act as much like a reality filter as a command center.

...but that doesn't prove anything about the existence of god.

Evidences, evidences, evidences, got any evidences god exist? No tangible evidences god exists whatever so ever.If I told someone i saw a unicorn and no evidences than no one would believe me.

Sure. There are at least six other dimensions that cosmologists have hypothesized. But they are curled in upon themselves. So what? What does that have to do with divinity?