Use images from posts in one category

I want to show the images from one post category as a gallery using WP Tiles. I have a category named jazz, so I think the short code should be:

[wp-tiles posts_query='category=jazz']

But, when I use that shortcode, all the images from all posts in any category show in the tiles up to the number selected on the defaults page.

As a test, I tried setting the default category to jazz using the simple shortcode without arguments and that works. So, it appears that I am not using the posts query arguments correctly. I want to be able to set up recent galleries for different post categories so I can’t depend on the default setting alone.

What am I doing wrong?

http://wordpress.org/plugins/wp-tiles/