I store my photos in a series of folders on my Mac named 01, 02, 03 and so forth. In GS I create folders with the same name as the Mac folders so I know where the original image and the watermarked version of each image is located. I batch watermark folders full of my images using iWatermark Pro to cut down on image theft.
Each of the GS folders is sub-dived into various other folders. In this example A to D represent various types of listing (auction, fixed, auction with fixed price), shipping (paid, free), and time period (7, 10 or 30 day). This allows me to quickly select groups of listing and change their type, shipping, or time period to correspond with eBay promotions. I do not pay listing fees, but list during the regular monthly promotions and promotions they have by invitation only thus I need a quick way to capitalize on these.
Sold items are dragged into the Sold folder - E in this example.
The folder named "----" (F in this example) is for items which I've withdrawn from listing on eBay for various reasons such as consigning the item to a retail shop; withdrawing for personal or business use; and so forth. Sometimes I combine items from two or more templates as a job lot so the unused templates are dragged here.
The items in the main folder, but not in a subfolder (G in this example) are partially completed listings. These typically include listings which I've completed everything but taking the pictures. Other items placed here have their pictures completed but their description has not been completed pending additional research. Once completed these will be dragged into one of the sub-solders.
I typically archive images to a hard drive using a hard drive dock periodically, deleting the watermark versions of images, which are kept in separate folders, as they can be remade. I also export old GS listings periodically to the hard drive. I reuse some of my images for art work thus I basically save everything. I still have a bunch of old listings stored on CD from 2000 - back then hard drives and RAM were expensive and CDs were the cheapest route to go.