More than a mere bedroom, it's the master retreat. A two-sided fireplace with brass stovepipe adds luxury to this spacious suite. Colors are muted, and decorative pieces are kept to a minimum for a soothing atmosphere.Spaces is a feature that showcases interesting decorating ideas for small chunks of space. If you know of a well-decorated niche, write to At Home, St. Petersburg Times, P.O. Box 1121, St. Petersburg, Fla. 33731.