To begin a defense of using icons or of venerating saints, the first objection that many will have is something along the lines of "its not in the Bible". This of course is a simplistic assertion of a much more nuanced and intellectual theological concept known as the "regulative principle".
The regulative principle can be summed up in the Westminster confession this way:
"The light of nature shows that there is a God, who has lordship and sovereignty over all, is good, and does good unto all, and is therefore to be feared, loved, praised, called upon, trusted in, and served, with all the heart, and with all the soul, and with all the might. But the acceptable way of worshipping the true God is instituted by Himself, and so limited by His own revealed will, that He may not be worshipped according to the imaginations and devices of men, or the suggestions of Satan, under any visible representation, or any other way not prescribed in the holy Scripture." XX1.1The idea is that anything not commanded by God in scripture is false worship. This became a classic concept in the Reformed (not necessarily Lutheran, and not Anglican) traditions.
Just a few arguments should suffice to show that this is a mistaken concept.
Musical InstrumentsAlthough the OT law is filled with regulations about worship, yet nowhere are the Israelites commanded to worship God with harp, or lyre, or with professional Temple singers. If the regulative principle was true in the OT, then we should expect all these things to be forbidden as un-commanded or at least only allowed after certain divine revelation commanded them. Yet instead we find:
"From the almug wood the king made supports for the house of the LORD, and for the king's house, lyres also and harps for the singers; no such almug wood has come or been seen to this day." 1 Kings 10:12 (NRSV)Wait…what harps and lyres and singers? Perhaps Solomon is sinning and God should judge him…
"Now these are the singers, the heads of ancestral houses of the Levites, living in the chambers of the temple free from other service, for they were on duty day and night." 1 Chron 9:33 (NRSV)Bad Levites! How dare they add to God's word by inventing ways of worship. They have appointed special singers and trumpeters for the Temple! But maybe God will send a prophet to correct them!
"all the levitical singers, Asaph, Heman, and Jeduthun, their sons and kindred, arrayed in fine linen, with cymbals, harps, and lyres, stood east of the altar with one hundred twenty priests who were trumpeters. It was the duty of the trumpeters and singers to make themselves heard in unison in praise and thanksgiving to the LORD, and when the song was raised, with trumpets and cymbals and other musical instruments, in praise to the LORD, "For he is good, for his steadfast love endures forever," the house, the house of the LORD, was filled with a cloud, so that the priests could not stand to minister because of the cloud; for the glory of the LORD filled the house of God." 2 Chron 5:12-14 (NRSV)Yet after all that, does God reprimand them for man made worship? Nope, he fills the Temple with his Glory and so shows his acceptance.
While on this topic two minor points should be noted, the book of Psalms was written over time, therefore, each new Psalm was a man made invention, even if it was inspired, God never commanded them to do it, yet he inspired them anyway.
TempleAlthough there were very detailed instructions for the Tabernacle, God never commanded anyone to build him a Temple. Yet when David decided to build one anyway, God accepted it! (2 Sam 7:1-17) Yes, God did remind him that he does not "dwell in houses made of human hands", and then proceeded to inform him that he would have his son build one anyway. God never commanded, but he did accept it. Furthermore, God never gave any direction in this, and unlike the Tabernacle gave Solomon the apparent creativity to add embellishments as would have been appropriate.
Purim/HanukkahIn the book of Esther, after the Jews are saved by the acts of Queen Esther they decide to make a memorial of the day of victory over their enemies:
"These days should be remembered and kept throughout every generation, in every family, province, and city; and these days of Purim should never fall into disuse among the Jews, nor should the commemoration of these days cease among their descendants. Queen Esther daughter of Abihail, along with the Jew Mordecai, gave full written authority, confirming this second letter about Purim. Letters were sent wishing peace and security to all the Jews, to the one hundred twenty-seven provinces of the kingdom of Ahasuerus, and giving orders that these days of Purim should be observed at their appointed seasons, as the Jew Mordecai and Queen Esther enjoined on the Jews, just as they had laid down for themselves and for their descendants regulations concerning their fasts and their lamentations. The command of Queen Esther fixed these practices of Purim, and it was recorded in writing." Esth 9:28-32 (NRSV)Queen Esther invented a Holiday, and it became a feast alongside the others commanded in Scripture and became part of Scripture without direct Divine authorization for doing so.
Even farther, Hanukkah never became recorded in Scripture, yet it is very likely that is what Jesus is celebrating in John 10:22-23, a man made religious holiday.
BaptismSpeaking of Jesus:
"Then Jesus came from Galilee to John at the Jordan, to be baptized by him. John would have prevented him, saying, "I need to be baptized by you, and do you come to me?" But Jesus answered him, "Let it be so now; for it is proper for us in this way to fulfill all righteousness." Then he consented. And when Jesus had been baptized, just as he came up from the water, suddenly the heavens were opened to him and he saw the Spirit of God descending like a dove and alighting on him. And a voice from heaven said, "This is my Son, the Beloved, with whom I am well pleased." Matt 3:13-17 (NRSV)Baptism was never commanded in the OT at all, this was definitely a latter development. A man made religious ritual to signify something God had never commanded. In fact God had commanded other ways to repent, via sacrifices. Yet Jesus not only endorses this man made religious ritual, but considers that he "needs" it to "fulfill all righteousness" which latter becomes incorporated into his Church.
Some will object "of Course Jesus can add to God's revelation, he is God." But this misses the point that Jesus was not the one to invent Baptism, it had already been invented without God's authorization, yet apparently with his approval.
ConclusionAnother example could even be the Apostles appointing Deacons, showing they felt no qualms of having to follow any regulative principle in Church government. I would even argue this applies today, and we are until little direction from Scripture on how exactly to run the Church, so long as general principles are not violated. Yet of all the general principles in scripture, the regulative principle is obviously not one of them. God has endorsed: man made places of worship, songs, worship leaders, additions (instruments), holidays and rituals by God's people.
Therefore, whatever may be said about veneration (not worship, which will be covered) of saints and of using icons, they cannot be objected to on grounds that they "are not in the Bible"