thank you for your excellent plugin. I had the need to associate multiple images to a post (in addition to choose the featured). I searched everywhere and couldn't find a solution so I decided to enhance it myself to allow that.
So simply add a collumn to the csv with the images you want attach to post, separated by a pipe (image1_url|image2_url|...).
You'll need also to modify SmackImpCE.php - see the diff here: _http://www.mergely.com/UMqIk4u4/
During import a post_images drowpdown option is availble.
Haven't tested it much but it's working for me.
Hope you guys can include it in the free version :-).