Is the universe simply a mass of atoms in 'void'; what does it look like? I've always been stumped with the question of what lies beyond the universe, and I've come to the firm conclusion - void (i.e. completely empty).  Does it make sense then to think of the universe as a finite 'blob' of atoms (the completely full) flying around each other in nothing?  Furthermore, and more importantly, does it have a shape like a sphere?
It is not known. The universe has a finite age so we cannot see beyond the speed of light times that age (and taking the Hubble expansion into account as well). This means there is a 'visible universe' which defines a boundary of what we can observe. Information does not travel faster than light. 

The whole universe is bigger than the visible universe, but we don't know how much bigger (it could even be infinite). However, as the universe contains all space ánd time, the stuff outside the universe does not contain both (try to wrap your head around that!) 

As I mentioned it could be infinite, we could live on the three dimensional surface of a four dimensional ball (like an ant on a balloon) or our universe could be embedded in a higher dimensional multiverse (like string theory tells us). 

We probably will never know because we cannot see past the visible universe.