As mentioned before, the Kepler - Attachment fields | simple & multiple custom field can be configured to store multiple files. 

Step 1:  Click on Attach files Icon   and select files.

Step 2: Choose one, or multiple files from the opening window or, drag and drop your Files.

Step 3: At this step, you can:

     1. Delete files from the custom field.

     2. Preview images or download other file types

Step 4: The Attach File Manager controls automatically the attachments according to the administrator's configuration, and displays error messages in case of files that do not correspond to the field configuration.

       Case 1: Files extensions are different from the configuration.

        Case 2: The sum of all sizes is greater than the defined one