Why should I have to hunt with my mouse for a certain vendor I want to find if I could just as easily locate it by having different icons? Hammer for hardware vendor, fork and knife for kitchen tools, beaker for alchemical, chicken or pig or whatever for animal goods.
It is not fun having to look at that little "C"-looking icon, mouse over it, find out it's not what I need, mouse over the next one, mouse over the next one, mouse over the next one, and then finally find the vendor I need in a tedious and ill-thought out process.
And while we're at it, wouldn't mailbox icons be helpful too? I know you devs might be up to this simple idea because of the new (thank god) subway icons that were implemented.