Personally, I love subtle texture in clothing. Hairline-striped dress shirts, chambray donning slight herringbone patterns, silk ties with lightly imprinted check shadows. I think the extra detail makes all the difference, and can transform a boring outfit into an awesome one, all without the pizzazz of more in-your-face patterns like plaid, tartan, or madras.
Subtly textured clothing can help spice up an ensemble of solids, or also tone down an ensemble of complex patterns. It occupies that versatile middle ground between patterns and solids, so I would suggest getting a couple textured pieces (ties, shirts, jackets) if you can. Not only will people start to notice your attention to detail, but you'll feel smug in the process, secretly knowing you've one-upped your style game.