Standardization of emoji usage

Not being a big user of social media, I was nevertheless fascinated by the uptake of emoji and its various forms (same with emoticons when it first caught on). I am wondering whether there has been any standardization on the use of emoji in general IM and online conversation in the same way emoticons were (although there were a lot less variations and styles possible).

By standardization I am referring specifically to three different areas:

• The type of applications (both within and outside of IM) where it is acceptable and common to use emojis
• The meaning of frequently used emojis (across different languages or cultures)
• The way emoji messages are constructed, i.e. the 'grammar' or 'syntax' (I get very confused when there is more than one used)