I could throw some of these together.
As for how to incorporate it into the interface, I would suggest two radio buttons: "text" and "symbolic". Selecting "text" enables the usual speech and thought, and selecting "symbolic" enables a drop down list of options, such as "idea", "angry", "confused", etc.
Okay... so, an "idea" light bulb, an angry storm cloud thingy, a bunch of shocked exclamation marks, a bunch of confused question marks... anything else? I was thinking a kind of "pop" pictograph, showing someone realising something (you'd know what I meant if you saw it). Oh, how about a bunch of swearing-substitute symbols for the prudes?
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