Error in creating XML Field for attachments

I have created an XML field 'AttachedImages' similar to 'AttachedDocuments' (K2 creates this XML field when using sharepoint multiple document event) and copied the XML schema from AttachedDocuments.

But I get the following error when I use this XML field in my event.

I get an error XML field's schema is not in the correct format to handle document attachments.

How can I resolve this error?

Thanks