This definitely falls under the heading of, "They didn't have to do that, but they did anyway.":

Snow Leopard has the ability to actually read backplane chip information on HDD enclosures (of which most have manufacturer-specific code on the boards) and translate that into a custom desktop icon for that connection. I've no idea just how many companies have been represented by custom icons but so far my FirmTek eSATA and Fibrenetix fiber enclosures both have custom icons with a photo of their branded hardware.

Totally unnecessary but very cool and can actually aid in visually seeing what's connected and what's not.

Upon further digging this "new feature" isn't part of Snow Leopard after all; it turns out these custom icons reside in the *driver* information supplied by the various vendors and Mac OSX simply recognizes the HBA card it's connected to, uses the appropriate driver and then displays the custom icon built into the driver software.

Otherwise, SL simply uses it's own built-in icons to display the various connectivity types, USB, FW, eSATA etc.

You can, of course, create your own custom icons for anything the Mac displays but that's a totally different thread topic.