Here are some emoji sets you could use to represent a business client, depending on the tone and context you want:

Professional & Neutral

• 👔 (tie — professionalism)
• 🧑‍💼 (businessperson)
• 🏢 (office building)
• 📊 (chart — business relationship)
• 🤝 (handshake — partnership)

Friendly & Relationship-Focused

• 🤝 (handshake — collaboration)
• 🌟 (star — valued client)
• 💼 (briefcase — work relationship)
• 📞 (phone — communication)
• 😊 (smile — positive rapport)

Abstract & Symbolic

• 🔑 (key — key client)
• 🎯 (target — target account)
• 💡 (lightbulb — opportunities)
• 🔗 (link — connection)
• 🏆 (trophy — top client)