I ran into this issue as well. There is a quick fix. Just change this piece of code to make it continue if an image is missing.
In \Libraries\Nop.Services\ExportImport\ImportManager.cs – change:
if (String.IsNullOrEmpty(picture) || !File.Exists(picture))
what if if I use nopcommerce 3.6
I have over 4000 products and about 80-100 of them are missing