I'm trying to do a critical revision of the famous sign clasification of Ch. S. Peirce (regarding the relationship between representamen and object): icons (likeness), indexes (contiguity) and symbols (convention). It seems to me that we should think in the other options: more sign classes or less sign classes.
More possible sign classes: a) Signs based on the fact that they uniquely belong to a unique object, it is to say, not interchangeable signs; b) signs based on the fact there is no object to link (is it possible?); c), d), etc.
Less sign classes: a) convention is absence of a natural relationship, not a real relationship between representamen and objec (only natural links are significative links) , and b) likeness could be reduced to contiguity.