Adding template images (e.g. referenced in the css) into Tridion one by one is time consuming. I there a tool that will upload multiple images at once?
This is also a tool in the Tridion PowerTools project
I believe it is working: https://code.google.com/p/tridion-2011-power-tools/wiki/BatchImageUploader
As an alternative to WebDav, the 2011 Power Tools project includes a Batch Image Uploader:
When using Dreamweaver, you could have it upload all your images referenced in your DWT templates by uploading the dependent files. Dreamweaver uses WebDAV for the actual upload, so the manual way of doing that would be to just use the WebDAV Windows Explorer interface (where you can drag and drop multiple files).
If you would like something else then the Batch Image Uploader in the Tridion Power Tools project would be an option
though I know others have already answered the question by suggesting Power Tools, I'd like to address something else.
If your need is specifically images referenced in the CSS file, then these images probably aren't 'content', are they? I would think that images called from CSS are presentational in nature, and will be called, therefore, every time a page loads; this can poorly affect performance for the end-user. Why not make a single image sprite, and load that file?
I know it would seem time consuming, but Adobe Fireworks CS6 has a sprite-making functionality, where you add all of the images, slice and name them, and it generates a CSS file for you and builds an optimized sprite. I've used it several times (in Tridion implementations) to save the burden of having multiple presentational images to manage in Tridion.
I realise that I'm a bit late to this party, but you may want to consider using @UI-Beardcore's MultipleUpload bookmarklet:
This is one of many bookmarklets submitted to the Tridion Bookmarklet challenge and is a great example of providing really easy to use functionality by extending the Tridion interface through bookmarklets.