If you have a single page tiff then it will only display one image. If you have a multiple page tiff then it should display a thumb for each page/image.
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ThumbCount Property
Returns the total number of pages present in the current image file.
Available With
Imaging for Windows Professional Edition V1.0, V1.1, and V2.0
Imaging for Windows 95 and 98
Imaging for Windows NT 4.0
Applies To
Image Thumbnail control
Syntax
object.ThumbCount
Data Type Long
Remarks
Available at run-time as read-only.
ThumbCount is recalculated each time a valid image is specified, or when either of the methods InsertThumbs or DeleteThumbs is executed.
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Granted, this is just the count property but I think once you start playing around with it you will be able to use it for ideas as mentioned before.
Good Luck