The Boston Symphony Orchestra opened the Tanglewood season Friday with a fancy affair at its summer retreat in the Berkshires. But before settling into the shed for an all-Tchaikovsky program featuring violinist Joshua Bell, guests enjoyed a Russian-themed party in an elaborately decorated tent overlooking Ozawa Hall. (Inspired by the designs and colors of Faberge eggs, the tent was done up with vibrant flowers, tables draped in purple linens, and walls covered in colorful silks.) Chef Lydia Shire created the menu for a guest list that included BSO board chairman Steve Weber and wife Dottie, BSO managing director Mark Volpe and wife Martha, singer James Taylor and wife Kim, BSO overseer Jill Hornor and cellist Yo-Yo Ma, BSO trustee Joyce Linde and son, Boston Properties president Doug Linde, and trustees Steve Kay and Nancy Fitzpatrick. . . . The night before, Taylor and his wife were at Tanglewood to catch Jackson Browne’s concert, and the old friends did a little reminiscing backstage.