When establishing a new church in an established space a group must re-create the architecture from the inside out.  The building looks same on the outside, but on the inside the room must take on the shape and purpose of the community inhabiting it, even if it is only for a few hours a day.

Architecture has been well explored as a function of liturgy and worship, even in evangelical churches, where the focus of most new buildings is to place every seat so it has an uninhibited view of the podium and the projector screen.  

Interior design has little significance for established churches, who have chosen a particular design, contemporary in its day, that is kept for the life of the church.  This stability is a good thing.  You can tell how old a church is by looking on the inside and seeing the design.  A church with orange carpet was made during the 1970s...that's a give in.

Art is needed weekly when setting up and taking down a church on a weekly basis.  Most church interiors are like one great painting: they are designed with great care and then preserved as best they can.  In the rental space my church plant uses, we have to recreate our group's space each week, and as we grow move things around and re-organize our space.  Our church is maleable, a new piece of clay that can be molded weekly.
This maleability of a meeting space was common for the early church.  They met in homes, in courtyards, in catacombs, and in hidden places.  They might not know where they would have church each week, but they were going to have it.

So the interior of the church became more important than the exterior, which could change depending on the needs or dangers the local church faced.  

This presents us with the question of interiority of a church: what is essential for a church to function on the inside?  If you were going to "do church" each week and could only take a few things, what would you have to have?

The table, the water, and the Word are essential for sanctuary to take place.  Church can happen when these items are present, for then community is formed around communion, around baptism, and around the Word.

Stripped down and laid bare, a service or liturgy needs the presence of these three symbols and elements, and then it can take place in a catacomb or in a magnificent cathedral.  The art of the sanctuary then, is found in the symbols that all church services hold common, and all other symbols should point toward these three.  Our prayers and songs should focus on communion and on the Word of God while reminding us of our baptism.  Our announcements remind us of our community and our place in the Body, found in our common baptism. Same too should the interior of the church point the community toward these symbols.  The interior of a church should point the congregation toward the table, toward the Word, and toward the water, which is why the altar and lectern are so prominent in older churches.  A critical eye needs to be used on a church that has a moveable altar that is taken away or dismissed when communion is not taken.  Flags, banners, windows or fancy Powerpoint and light shows must never supersede the primacy of Word and Sacrament.  Whether the wonderous artwork of a cathedral or the simplicity of a rented room, the decor must push us toward God.

God is found in the common symbols, for these are the tools we use to do the public work of serving our Lord.  We must remember them, we must focus on them, and they must be the center of the church, so that no matter what clothing a meeting place wears, its heart will be clean and its worship abundant.