Because the Pet industry has numerous categories the user needs to be able to search by category; Emergency, Veterinary, Pet Clinic, Groomer, Boarder, etc... I built out my (Listings -> listing-categories) and found that I could not have different icons for the various categories. I set new icon color and icon, and it doesn't show up on the map. on a national site I manage I have custom icons for each category that are unique and have unique colors, which makes for nice branding. For people who don't know where the local pet facilities are around their location, this helps them to distinguish a category without having to click on each and every icon.