I am putting together a map of GPS-enabled vehicles, and I am hoping to display them with custom point symbols that change appearance based on a few attributes (things like velocity, heading, and a few other business attributes). For example, the fill color might change depending on the vehicles speed, the shape might change based on vehicle type, and the size might change based on another attribute. I have considered using the 'unique values, many fields' option in the symbology menu, but I don't think it will work for this task because 1) my data has seven attributes that the symbol needs to be based on, and the dialog only allows for three fields, and 2) if I have to create each symbol individually for every combination of attributes, I'd have to build over 350 symbols in total. I would prefer to specify something like 'if speed is X, set fill color to Y, if vehicle type is A, set symbol outline to B, etc.' One option is to create the symbols using labels rather than symbology. Simply setup a label that is rendered on top of the point and use a transparent marker symbol. Using the label expression you can create different symbols depending on field values by changing the labels character. The size and colour can then be changed using formatting tags. This approach can work well, and is easy to setup. However, if you use the default labelling engine you may have problems with closely packed labels. It also limits you to using a single character as your symbol. EMF format is the only vector format symbology I can find documented supported in arcgis. There is the cartographic representations that 'looks' to be a vector format. But I can't see any documentation on what format it is. If you look in the style manager, you will see the representation markers. None of the standard esri have any populated symbols in this category. Your personal style will have just a handful. If you search for other questions with 'representation' there are some pretty detailed descriptions of the limitations and uses. Source.