Mosques are often really plain, and they never have pictures or sculptures in, though the more important ones are decorated with amazing mosaics. Muslims kind of believe that we should not try to copy God's work by drawing people, so that's why you find that Muslim art is mainly patterns, like on rugs and mosaics. We also really strongly believe that we can't imagine what God is like, so you'll never find any pictures like the ones I've seen in churches, and I know Hindus have loads of statues and pictures of their different gods.