When you're sending an email to your colleagues, sometimes an emoticon or two will be appropriate, but if you fill your emaisl with faces and other images, you are going to look like a little immature, or even worse as a person who does not know how to express their thoughts.
We also have the social network pages of your company. Sometimes an emoticon can serve well for your posts, but in my opinion it should never be anything other than a smiley face. The winking face and the sad face are even less professional and your pages will be left looking like a childs school project.
It really makes no difference if your clients are your friends or not, emoticons have no place in your professional messages.