Decorating a church service is a careful, respectful process. Before doing anything, you should contact the local Altar Guild to check on specific requirements. Arrangements for the altar require a reservation. There may be height and width restrictions. There may be special, water-proof coverings required. There may be special restrictions on how and where you can place floral decoration. You may not be allowed to hang arrangements on the edges of pews or in windows. There will almost surely be restrictions against using nails or glue to affix items to the structures in the sanctuary! Don’t assume anything.
Most churches frown on the use of artificial material. There are practical reasons Christmas wreaths and garlands must be artificial, since they will be on display from late November to early December, but even when artificial greenery is allowed in certain areas, it may not be in all. Many churches do not allow artificial, taped music, much less silk flowers. Typically, anything beyond the altar rail must be live of dried, real plant material—no plastic!
Lighting and candles can get tricky, too. Most altar guild members have stories to tell about damaged caused by candle wax or flames. The simple act of blowing out a candle can cause molten wax to spew across priceless furniture and expensive fabric. If you plan on using candles or electrical receptacles, check first with the altar guild, and be prepared to explain how you will protect items nearby.