The only thing outside of the universe is nothing, however nothing also exists inside our known universe between the gap of what is and what is not. The expansion or so thought of explosion. I believe was actually a collapse of everything. Which created nothing that is expanding in between what is something. The further your perceive to go outward from your current location the more nothing you are just putting between you and something. As you theoretically travel further you are actually collecting more nothing which is why something such as time since you were there increased buth there is more nothing now and less of anything but your perception of when.
I think that the known universe is just a small part of what is really out there. There is so much we do not know about things outside of our own planet that it is silly to think that the universe, as large as it is, is the only thing out there and that it is all encompassing.
I believe outside of the know universe is more universes. These universes would have a different set of law and dimensions ranging up to 11. This is also know as the multi-verse theory. The universe is so huge as it is, and so many amazing things exist. Why would we not want to believe in even crazier and amazing things?
I believe that the only thing that exists outside of this Universe is God and his wonderful place of Heaven. God created all that we live in but there is a Heaven that we can go to when we leave this place and it is one hundred percent perfect, like God himself.
As someone who is religious, I believe that the universe is not everything, but is what we can see that is of this dimension, so to speak. It's difficult to know how to word that without sounding like a science fiction term. I believe that there is also a spiritual realm, so that there are things we can't see and that don't necessarily exist in the universe as we know it.
For me it is hard to sit here and say that the universe encompasses everything because by doing that I feel like I'm saying yes, somewhere out there, there is a huge proverbial wall and that is the edge of the universe. To me, that doesn't work, so I feel like there is more beyond the known universe.