Are link images/banners usefull?

[jaffstar]

Do images/banners that are linked to other sites count as much as anchor text links?

Would the following influence the above:

1. Alt img tag
2. domain name, ie
href="www.keyword1-keyword2.com"><img src="image.jpg"
3. image name, ie. keyword.jpg.

Surely if you wanted to rank for :keyword1 keyword2
href="www.keyword1-keyword2.com"><img src="image.jpg" ,would count the same as :

<a href="www.domain.com">keyword1 keyword2</a>

[jaffstar]

Anyone?