Sherlock's clearly got a thing for jumpers.
First Impressions
John was sure he'd be lost in this house before long. Mycroft knew his way around easily (not that John was surprised). They soon encountered Sherlock, examining an intricately embroidered lampshade.
"It's time for dinner," said Mycroft peevishly, straightening the tilted lampshade as Sherlock stood. As usual, both Holmes brothers were wearing suits, but John suddenly felt a twinge of concern.
"Am I underdressed?" he asked.
"Everyone will be arriving in whatever they choose to arrive in," Sherlock said vaguely. "Don't change." He looked a little embarrassed. "This…this is how I want them to see you for the first time."
Prompt was from my sister, Seaton, and it was "Lampshade."