Product images can be managed in several ways. Go to the setup card and you will see that there are 3 different options. 

Database, External and Azure Storage - File Share. 

For smaller catalogues

Database is the standard value, and this means that images will be stored in the Business Central SQL database (BLOBs). This works fine for smaller Magento catalogs. For example if you have 1.000 items with 2 images each, where the average image size is 250 Kilobytes. Then the sum is: 

1.000 x 2 x 250 Kilobytes = 500.000 Kilobytes = 500 Megabyte = no problem for your Business Central database. 

A standard Business Central SaaS SQL database is 80 Gigabytes by default. 

When working with the Database option for images, you can simply drag and drop images on to the blue plus sign on the item card and they will automatically be uploaded. First into the Business Central SQL database, and as a next step they will be synchronized with Magento as well. 

Please note that you can drag and drop multiple images at a time. 

Working with larger catalogues

If you have 50.000 items which all have 10 images that are 1 Megabyte each. Then the calculation looks like this: 

50.000 x 10 x 1 Megabyte = 500.000 Megabyte = 500 Gigabyte = a big problem for your Business Central database. 

For these scenario's you want to look at the other options, External and Azure Storage - File Share

External means that you will be working with external URL's. This means that your product images can be stored anywhere on the internet. Once you switch to using external URL's, you cannot drag and drop files anymore. Instead the External Content URL field will become visible when you navigate to Content > Images. This field can be used to either enter data manually, or you can use BC Configuration Packages (Excel imports) to quickly import many image at once. 

When using Azure Storage - File Share you will indirectly also use the External Content URL field, but then in a different way. To use this functionality you first need to have an Azure Storage account that contains a File Share. Once this is in place, you can enter the authentication credentials for this File Share on the Setup Card. And then you can synchronize the contents of the file share location with Business Central. 

One of the advantages of using Azure Storage - File Share, is that you can easily create a virtual local drive that allows you to manage images as if you are working directly on a local computer. 

To map your Azure File Share, go to the Azure portal, navigate to the File Share, click Connect, and then create the right Powershell script for your situation. 

Once you have executed the Powershell script to map the File Share to a local drive, you can manage your images like in the screenshot below. 

When working with Azure File Share, make sure that you always create a folder per item number. 

Once you are ready adding new files, click the import button on the Setup page again.