Import from Excel stops running if image is not found on server

I think it will require customization.

Ok it looks like I've been able to find a fix for this. Please look at Libraries\Nop.Services\ExportImport\ImportManager.cs in the ImportProductImagesUsingHash function. In there you will see the following code

foreach (var product in productPictureMetadata)
            {
                foreach (var picturePath in new[] { product.Picture1Path, product.Picture2Path, product.Picture3Path })
                {
                    if (String.IsNullOrEmpty(picturePath))
                        continue;

Change it to the following

foreach (var product in productPictureMetadata)
            {
                foreach (var picturePath in new[] { product.Picture1Path, product.Picture2Path, product.Picture3Path })
                {
                    if ((String.IsNullOrEmpty(picturePath)) || !File.Exists(picturePath))
                        continue;

You may have to make a similar change to the ImportProductImagesUsingServices function as well.

Good luck!