In addition to an automatic thumbnail creation feature, the ASPxFileManager allows you to provide custom thumbnails by handling the CustomThumbnail server event. This event allows you to define a custom manner that determines how all or certain files should be visually represented in folders. Within the event's handler, the currently processed file can be accessed and identified by using the File property, and a custom thumbnail can be defined for the file via the ThumbnailImage.Url property.
In this demo, the CustomThumbnail event is handled to analyze file extensions and represent each file type using the corresponding custom thumbnail image.