Help: Inventory Bulk Image Upload
To easily add images to inventory items, click on "Inventory" on the left hand side and then click "Bulk Image upload"
You will now see a list of Inventory items that don't have image associated with them.
You can now drag images into the "Drop here to upload" section and it will upload the image and remove itself from the list.

Repeat until done.
If you don't have an image for some items, you can press the 'Next 5' link to skip them.