Hi rstocks, glad you like them :)
While I don't have an option for this available (yet), it's something that I've thought about a little bit and talked with some friends about.
Because of how it imports the media (using media_sideload_image()), it actually requires a post to attach it to, although could potentially be changed. In the meantime, you could change it so that the posts it creates are only Drafts maybe?
To do that in the Flickr importer, make sure you're using the latest version, then change line 188 so that instead of:
$post_status = 'publish';
$post_status = 'draft';
You'll still end up with a new post for each image, but at least they won't be published. I'll take a look at how hard it'd be to just import images to the Media Library instead.