The box could represent being "of" versus "in" the world, a scripturally based concept.

“Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him. For all that is in the world – the lust of the flesh, the lust of the eyes, and the pride of life – is not of the Father but is of the world. And the world is passing away, and the lust of it; but he who does the will of God abides forever.”

--1 John 2:15 (Holman Christian Standard Bible)

For the grace of God has appeared, with salvation for all people, instructing us to deny godlessness and worldly lusts and to live in a sensible, righteous, and godly way in the present age, while we wait for the blessed hope and the appearing of the glory of our great God and Savior, Jesus Christ.”

--Titus 2:11-13 (Holman Christian Standard Bible)

This is important because the box is a limitation for the figure and the above scripture references imply that becoming too caught up in the world can lead to the loss of a life-giving, loving, meaningful life. Loving God and loving people equals a life full of relationships not objects. In my "box" series the figures are veiled and blinded by an object. The box appears to read as a barrier that the figure cannot, chooses not, or naively doesn't recognize the need to escape.