As the seventh Ecumenical Council (787 A.D.) restored Icons in the church as objects of veneration, the Church Fathers emphasized the visible form of God’s revelation to humankind.
The prototype of the Icon is God becoming human form in Jesus Christ, i.e. visible to our senses. So are his mother, the Theotokos, and all the saints, including biblical themes and events depicted on Holy Icons for our edification and thus being a tool to salvation.
Holy Scriptures (Bible) themselves are iconographic, just not pictorial but in form of letters, words and sentences. This was less of a value until such times (a few centuries ago) when the average person was actually able to read. Until then, Icons were the powerful way to convey God’s word to humankind.
Most importantly, God gave us all our senses to comprehend His message, such as through incense, church music, the taste of His Body & Blood (Eucharist), Icons, art — all given to us, so we may grasp His wisdom.