First Kings 7 shows the work that Solomon had done for the Temple of God. Since Solomon built the temple for God, we might be tempted to over-interpret everything associated with it, such as the following,

He made a lattice network, with wreaths of chainwork, for the capitals which were on top of the pillars: seven chains for one capital and seven for the other capital (1 Kings 7.17). 

Yet, the two previous verses say,

And he cast two pillars of bronze, each one eighteen cubits high, and a line of twelve cubits measured the circumference of each. Then he made two capitals of cast bronze, to set on the tops of the pillars. The height of one capital was five cubits, and the height of the other capital was five cubits (1 Kings 7.15–16). 

What is the spiritual significance of two or five? Yes, sometimes seven in the biblical does have special meaning, but I do not believe that it does here.