Tetelestai means "It is finished." The last words of Jesus on the cross. Can there be any more powerful, soul-nourishing phrase for the Christian? This design is meant to invoke victory of death and sin. And is also super cool. Hang this somewhere where you can be reminded of this beautiful truth each and every day, as often as possible.
This phrase is the lifeblood of the believer. Christ has conquered everything necessary for us to know God, know the Father. It is all done. You don't need to do anything. Believe it. Rest in that.