I get really frustrated that the Nextgen plugin for WordPress does not have a simple icon which allows a quick way to insert a “single” image from the gallery. The options in the “Add New Post” screen only seem to allow a whole gallery to be selected…
This is how to add one image to a post manually (provided you know the image ID)
There are some other shortcode options available here Nextgen Shortcode.
singlepic id=XXX float=