Putting it simple here are words to consider in your choice and suitability of banners:
1. CONTENT
2. COLORS and FONTS
3. LAYOUT
4. IMAGE
3. PLACE
4. BUSINESS CLIENTELE
May I suggest that you don't use the same banner all the time. You don't want to drive people away with seeing the same thing over and over. A new one at times would be very attractive and eye-catching.
