In 1.1 (hidden) and in 1.2 (no longer hidden) of dasBlog, you can enable a feature for Mail-To-Weblog that will automatically turn attached pictures (not embedded pictures) into thumbnails in the post and you can also control the maximum height for the thumbnails. The relevant settings in site.config for 1.1 are
<Pop3InlineAttachedPictures>true</Pop3InlineAttachedPictures>
<Pop3InlinedAttachedPicturesThumbHeight>200</Pop3InlinedAttachedPicturesThumbHeight>
In 1.2 the config settings are the same, but I added them to the config page. Here's an example of how it comes out:
