Well just as soon as I say that there is no way that you can add tags to the Windows Live Writer, there is a plugin to do just that. There are in fact 2 plugins available that I know of:
Add tags for Technorati and many other tagging services, but honestly Technorati is the only one that matters. I am testing out how well it works with this post.
As you guessed it, this allows you to add Flickr images from any username or tag. Quite useful for quickly searching for a picture to be added to your post.
There is also a Currently Listening To plugin, but I honestly never felt the need for this on a blog post.