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:

Tag4Writer:

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.

Flickr4Writer:

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.

Technorati tags: tags, technorati, windows+live+writer, live+writer, microsoft, post, wordpress, ultimate+tag+warrior, blog, post, flickr, plugin