Not all bridal showers need to focus on the styles and trends pertinent to today's weddings. Sometimes, a little nostalgia is called for, and there's nothing more fun than having a throwback theme, with decor and attire all paying tribute to decades past.
Depending on the bride's individual tastes, your theme may revolve around the '80s or '90s or go back as far as Greco-Roman times. Whatever your vision, don't be afraid to go all out - warn guests early with a bridal shower invitation instructing all attendees to dress to impress.
As for setting up the event space, read up on historical pieces that might give you hints as to the predominant styles, food and drink of the period. A 1950's theme might feature more pastels, pinks and bows than, say, a '60s party.
If you can't locate unique vintage items to offer as bridal shower favors, an easy solution is to think of a period-appropriate cocktail. Your Prohibition-era soiree may call for mini cocktail shakers, while something a bit more '40s-inspired may be the perfect occasion to offer guests mint julep cups.