why are there so many carved and cast images?Actually, I don't think there are that many, it just seems like alot in comparison to the stark minimalism of most protestant denominations. If you don't mind me saying, I think the better question (the one you probably had in mind) is this: why have images in the first place?
For one, before Christians became a predominately literate people, images were used to help teach them about salvation history and about the life of Christ. That was one reason for stained-glass windows and paintings and statues in churches. Even today, they teach our children about the mysteries of God and his Church, and for those who can read, they still work as a reminder of all that God has done for us.
Pictures and statues of saints in particular are reminders that the saints are always with us. They are the great cloud of witnesses (Heb 12:1) who cheer us on as we run the race towards that imperishable wreath (1 Cor 9:25). It is good to know that they are there, and that they are always praying for us. They know when people treat us with disdain (for they always behold the face of the Father, cf. Mt 18:10) and the Lord has charged them to guard over us (Psa 91:11).
Images in churches also reflect the belief that our liturgy is a participation in the heavenly liturgy seen in the Book of Revelation, where the saints stand in perpetual worship of the Lord. These images are a reminder that the saints are present, worshipping with us. Together we pray the Sanctus ("Holy, Holy, Holy" cf. Rev 4:8), the Gloria (Rev 15:3-4), and the Great Amen (Rev 7:12). Together we partake in the marriage supper of the Lamb (Rev 19:9).
On a more basic level, we are visual people. Sometimes it can be difficult to believe in or have solace in something we cannot see. God knows this, and he has done much to accomodate our "human-ness," first and foremost coming into our world in the person of Jesus Christ. He took on visual representation, which is one of the greatest defenses for images of Christ. Likewise, when we see the saints, it is easier for us to take solace in their prayers and they act as a reminder that we too can be saints as long as we model our lives after them.
do you believe these properly represent the way Jesus, Mary, Peter, Paul.... looked like?Well, it depends on the image. Some of the images you see have been "Americanized" so that Jesus and the saints look like Caucasians, which has always bothered me a little. But, our ancient Eastern icons are wonderfully beautiful and utilize traditional representations of Jesus and the saints. There are actually traditions regarding how certain saints look, so that they always look the same, no matter the artist. We may never know exactly how they look, or what Jesus looked like, but that's ok. The endeavor is a pious one, and it is meant to make Jesus and the saints more real in our lives.
I hope that helps.