What would be a good way to organize herbs and seeds for an online business?
Your enemies are going to be moisture, sunlight and changing temperatures. (really warmth mostly)
Old file cabinets, take an add out in craigslist offering to haul someones old file cabinet away. Find the local 'catholic charities' resale outlet or their associated organizations outlet. I point to them specifically because in most markets they work very closely with the discount office furniture stores.... so you can find really good deals on really rusted out file cabinets.
Contact your local library, good chance they are sitting on some old bibliography files. (or whatever those things are called.) Old 'flat' files might work, the type blue prints or diagrams used to be kept in ... they are about 2 to 3 inches tall by 4 to 6 feet wide. usually 10-15 drawers per section.
Of course you could just build an inexpensive rack out of some slat boarding, or salvaged fence sections. This rack should have angled and step-ed shelves that allow clear access to the box of seeds. And then just bulk store the inventory and pull out 'pick' boxes to replace the ones on your shelf as necessary.
You could just cut a 'hand hole' in the end of your bulk boxes, stack them all on top of each other and just reach through the face to pick your order. (heavier/bigger to the bottom please.)