Loki Software has released an updated version of its Mail Attachments Iconizer plugin for Mail.app, an add-on that offers much greater control over the way that attachments are displayed and packaged.
I could type out all the benefits which the plugin offers, but thankfully the developers have knocked up their own chart of improvements:
The new version adds some welcome features — a new option to always display full attachment names, the ability to images in HTML layouts of incoming messages in LEopard Mail, the printing of attachments according to how they are currently displayed on the screen and better recognition of images without filename extension.
It also offers a more reliable fix of interaction with the stationery feature in Leopard Mail.
Mail Attachments Iconizer is shareware (USD 14.99) is available from the developer’s web site 
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Why not just control-click on the attachment, and select whether or not you want it to display inline or as an icon? It’s not that hard.
C’mon, man, don’t you get it?
It’s not all about it. Think you receive like 20 pix in your mail, each of 2 MB. How long will it take to show everything? This plug-in makes mail show you just icons. Great app, very useful.