In ezmultiupload.ini.append.php, you can set up available file types for uploading per class or/and subtree node.
The default settings are the following:

<?php /*
 
[MultiUploadSettings]
 
AvailableClasses[]
 AvailableClasses[]=folder
 AvailableClasses[]=gallery
 AvailableSubtreeNode[]
 MultiuploadHandlers[]
 
[FileTypeSettings_folder]
 
FileType[]
 FileType[]=*.odt
 FileType[]=*.flv
 FileType[]=*.xap
 FileType[]=*.doc
 
[FileTypeSettings_gallery]
 
FileType[]
 FileType[]=*.jpg
 FileType[]=*.png
 FileType[]=*.gif
 
*/ ?>

"AvailableClasses[]=folder" and "[FileTypeSettings_folder]" is a pre-defined set. Therefore, with the default setting, the node created by “Folder Class” can upload only ".odt file", ".flv file", ".xap file" and the ".doc file".

Here is an example of using AvailableSubtreeNode.

<?php /*
 
[MultiUploadSettings]
 
 AvailableSubtreeNode[]=69
 
[FileTypeSettings_69]
 
FileType[]
 FileType[]=*.jpg
 FileType[]=*.png
 FileType[]=*.gif
 
*/ ?>

"AvailableSubtreeNode[]=69" and " [FileTypeSettings_69]" becomes a pre-defined set. Therefore, the node (node_id=69) can now upload " .jpg file "," .png file " and " .gif file".

The Filetype settings can use the regular expression.