I discovered something I didn't know about SharePoint. Picture Libraries create thumbnail and preview images of TIFF files.

If you want to render the TIFF images using a Data View Web Part, you need to calculate the url for the thumbnail or preview images.
For a file name of http://www.wssdemo.com/TIFF/PCR2.tiff

Thumbnail url = http://www.wssdemo.com/TIFF/_t/PCR2_tiff.jpg

Preview url = http://www.wssdemo.com/TIFF/_w/PCR2_tiff.jpg

You can create the preview image using the following in your rowview template section

<td class="ms-vb">

<xsl:variable name="PreviewURL" select="concat($HttpHost, ddwrt:UrlDirName(string(@FileRef)),'/_w/',ddwrt:UrlBaseName(concat($HttpHost, @FileRef)),'_', ddwrt:GetFileExtension(concat($HttpHost, @FileRef)),'.jpg')" />

<img src="{$PreviewURL}" />

</td>

To use the $HttpHost variable you need to add the following after the <xsl:stylesheet line near the top of the web part

<xsl:param name="HttpHost" />

Demo page

Imagine using this to store scanned images of invoices and then allowing someone (or an automated OCR process) to update custom metadata columns for the item. You could even create a linked data source to your finance records to show a single view of purchase order and accounts payable information including scanned images of the packing slip and invoice.