We've all heard the saying that first impressions are the most important. When you meet someone for the first time, what you think of them in that moment will stay with you forever and will shape how you view them thereafter, no matter how the person (or you) changes. I honestly think that's why a lot of people have bad experiences with church early in life and never come back when they're older. The God they were introduced to was hateful and petty, and no matter how hard we preach about the love of God or His goodness, they'll never see it. We gave them the wrong first impression.
This applies to the church building itself, too. I personally have problems accepting the true depth to which appearances matter, but the simple fact is, they matter tremendously. People have a hard time worshiping in a place that's too dark, too outdated, or simply doesn't have the proper space. If the first thing someone notices when they enter a building is how decrepit the walls look, odds are they're going to be skeptical of the rest of the service as well. Those first impressions matter greatly.
But I want you to remember this: no matter how you look as a church building, what matters more is Who is inside. One church I visited made my skin crawl the second my feet hit the tile inside the door. The building was well lit and a fairly recent construction. The paint was a pleasant shade, the stained glass windows were beautiful, and I literally went home and took a shower to scrub it off of me. Something was terribly, horribly wrong with that church; you could feel instantly this was a place the Holy Spirit was not, but something else was there instead.
Paint the walls, buy new carpet, do what you need to do to attract people and make them feel comfortable. But the presence of the Holy Spirit counts for more than anything.