I've always practised the art of making both the alt and image filenames as descriptive as possible. Why? Well, if you get an image get a top rank in the image search, watch your traffic shoot up. I've had a couple of nice ones go front page, and seen thousands of surfers come in via image search.
In one instance, a top image ranking bought me 30,000+ extra visitors over a 3 month period. So IMO they are very important for
SEO purposes, as lets face it,
SEO is about getting both rank and traffic.
I recommend going to these sort of lengths:
path: /images/celebrities/johnny-depp-portrait.jpg
alt: Johnny Depp portrait shot - sat in chair with beer
path: /images/cameras/nikon-d50.jpg
alt: Front view of the new D50 DSLR by Nikon
As well as the
SEO benefits, don't forget that you're also helping out those with screen readers.
