In stead of a mix of every possbile tetras, I would strongly suggest only 2 big schools of two tetra species. Believe me, it will look amazing!
For example neon tetras are amazing as a school of 30! And to fo with them, how about a school of tetras of complitely different color and shape. Like lemon tetras. They often seem rather pale in the fish stores but in a school of 10-16 and good tank conditions where they feel comfortable, they are really pretty in good colors!
The thing with schooling tetras is that when they feel comfortable they spread out all over the tank, when they are frightened they stick tightly together.
With a good proper school they feel safer and spread out better, because "wherever they look", they see one of their kind.
So they will show good colors and natural and brave behaviour. This is why you should always have a group of each species in stead of 2-3 of several kinds.
Not all tetras school however. For example emperor tetra males each choose their own area which they watch and will chase other males away from, while also trying to lure the females towards them. In such a case, 1-2 males and 3-4 females will do.