It is possible to place images in certain places when using plain text emails by using the #img# directive in your mail text.
Example
Here is a sample plain text email.
#img1#
With an image displayed in the middle of the text.
This will generate a post with the first attached image between the two paragraphs.
The number following #img directs Postie as to which image it should use. You do not have to use them in order. I.e. you can have #img3# before #img1# in your email.
Additionally you can specify a caption like so:
Here is a sample plain text email.
#img1 caption='pretty kitty'#
With an image displayed in the middle of the text.
Note you can only use the #img# feature if your “Preferred Text Type” is set to “plain”