It generates interest - There's this memorable scene from the movie European Vacation where the Griswold kids, Russ and Audrey, are trying to watch TV in London. They are completely disgusted to find that every channel is showing the exact same documentary on how to make cheese... The sad thing is that some churches have been "making cheese" for years... limburger cheese at that! But face it, the staff and members are tired of looking at the same old out-dated paint and paneling. Those that aren't tired of it don't ever really notice it. What they would notice is a fresh coat of paint, new drapes, something that highlights the message, or anything that breaks the week after week visual monotony. Long-term uniformity stifles growth and fosters apathy. "Stifling" and "apathetic" should NEVER be words to describe the church.
It gives creative people an outlet for their gifts - You've probably got several people who've been gifted with a talent for graphic, artistic, and interior design. Let them know what you're going after in your messages, encourage them, fund them, and let them go to work! You may have to provide some direction for some people (i.e.- remember the environment complements the message... it doesn't drown it), but in the end it's well worth it! One more word... pastor, unless you have a degree in art, DON'T MICROMANAGE YOUR ARTISTS. Let them pick the paint!
It helps keep pastors from becoming slack! - Face it... It's far too easy for pastors to become lazy. After you've spoken to the same group of people for a little while, you have a tendency to lose a little of your edge. You don't push yourself as hard to prepare. Your messages are tired and you become jaded. You fall into the "catch phrase" trap where you learn to string a few words together in order to evoke an "amen" or two. But... there's really nothing fresh to your messages, because you don't challenge yourself anymore. Now, changing your stage design won't do anything if laziness is a natural part of your character (If it is, you need to get out of ministry now!). But for the pastor who's willing to push himself, a group of creative minds who work along with him to alter the worship environment is a gift. You knows these people are working hard to complement the message God has given to you. You know you have to step up your efforts in preparation and execution, because you're no longer a "one-man show" when it comes to proclaiming the gospel on Sunday mornings. You've got an entire team that have designed, built, painted, and assembled (for God's glory) a fresh environment for the gospel to be proclaimed. You'd better be on top of your game. You'd better have prayed like a Calvinist, and prepared like an Arminian. Your role as a leader in preaching the Word absolutely demands it! That whole Iron sharpening iron thing...? It really comes to life in an arena that's constantly being updated to drive home the gospel.