You can upload artworks with Xpiks to any FTP server, including those which are owned by microstock agencies.
Select artworks that you want to upload and press “Upload” button. You will see an upload dialog where you should fill in various details like address, username and password for FTP. You can test if your credentials are valid using “Test connection” button.
Xpiks saves your credentials in secure manner and also allows you to set master password. You can read more about security here.
In order to add few upload hosts Xpiks can autocomplete stock name (even with fuzzy matching) and insert FTP address for you.