You're right. There are times when icons behave like message_keys as much as anything else.
Yet, image tags are different whether publishing html or xhtml. In a proc or template, making one change would affect all cases, but I don't see how to do that with acs-lang.
If icons will be added to acs-lang, could some kind of guideline about html use be added to the acs-lang docs, ie to keep appropriate usage practices? I can see where abuse of this feature could lead to whole web pages defined in it.
