Congratulations to your cousin! Decorating for a wedding with a vintage-modern twist sounds like a fun, but challenging task. While I don't know specific San Francisco decoration companies, have you considered browsing local event rental companies? Sometimes they have in-house designers or preferred vendor lists. Also, websites like Etsy can offer unique, handcrafted decorations to supplement a company's services. Think about incorporating a fun activity; maybe even a Snow Rider 3D game setup during the reception for something unexpected! Good luck with the planning!