Scribus sla files are the common file type to exchange documents in my forum.
Have to be renamed from *.sla to *.sla.txt to be uploaded
osp is the standard for video editing files.
In general, there should be no restrictions on file types at uploading.
There should be an array of allowed file extensions in your config. Check conf/config.php for $Configuration['Garden']['Upload']['AllowedFileExtensions']