Every bride plans a wedding theme for her big day but the ones who are lucky enough to have a church wedding are often faced with certain restrictions that brides getting married at hotels or some outdoor venue won't normally have. The thing about a church is that, it's first and foremost a church and it's not likely that you'll be allowed to make a whole lot of alterations according to the theme.
For most churches, you can use fabrics and flowers to decorate the pews and maybe the aisle runner. Any other change will have to be cleared with the church itself. A simple way to have a church wedding and be able to decorate it more is to have one in the church garden. The environment is pretty much the same but it's likely that you'll be allowed to make more changes.
You can opt to exchange vows inside and simply have the reception outdoors. Since the ceremony venue and the reception area are in close proximity; you can decorate your heart out on the reception. It's best to keep things simple and use simpler props like trees and arches. Use fabrics to emphasis a color scheme and avoid using candles.
Make sure the food is easy to serve and you don't need too much table ware. Not all churches have enough space for a big wedding reception and if you need to squeeze some tables in; you'll have to make sure the table isn't cluttered. Keep the centerpieces simple like fresh fruit arrangements or fruit bouquets. They can be the dessert and a unique part of your wedding arrangements.