I am in agreeance with you regarding alt attributes. I would think it is appropriate to leave ‘decorative’ images with empty alt attributes.
An example of a good time to use alt attributes is when using an inline image heading:
<h2><img src="heading.gif" width="70" height="14" alt="About"></h2>
With large scaled sites as you already know using css to declare background images can become rather messy and bulk the css file up.
Why not just fill your whole page with such garbage so that everyone gets to see how little you know about the web instead of just those who don’t see the images getting the garbage.
Anything you don’t want anyone to see that you are trying to use for your misguided black hat SEO efforts MUST go in the head of the page.
Use the new Dreamweaver; it always prompts me when I place images on the pages I’m creating. That way, I never forget.
And for people who use readers just to add accessability…
alt tags are picked up by search engines so well worth including. Not sure about decoration but it should still work as I doubt spiders are able to determine what the image is actually about?
For the umpteenth time: there is no such thing as an <alt> tag. It’s an attribute. Say after me: a-t-t-r-i-b-u-t-e.
Worst. Advice. Ever.
Do you really think it’s fair to sacrifice the usability for some users just to attract undeserved traffic to your spammy site? If you can’t get visitors with organic content, attracting them with fake text equivalents of decorative images isn’t the way to go.
Techically there is an alt tag, though its not called alt, its called noscript 
That doesn’t give alternative content for images, though. Only for scripts. 
Yes I know that Tommy, I was just trying to be humerous! 
I know. I was just stating the obvious in case some unsuspecting beginner stumbles over this thread sometime in the future.