Silver tip tetras are pretty active tetras. Congo tetras are pretty and they get about 4" so would be compatible with the 3" tiger barbs...but how big is this tank? If it's the 29...the barbs wouldn't work out eventually. Neither would the congos because of size and definitely would be problems later with the gouramis. They get big too and gouramis, like tiger barbs are semi aggressive fish and demand their space...particularly with their own kind, but not limited to.
Other nice tertras are the emperor tetras, diamond tetras, black phantom tetras, and bleeding hearts. These tetras don't school as tightly as many other tetras and instead hang out loosely amongst each other forming pairs. The silver tip tetras are as active as danios and form tight schools.