Selected answers from the Dumb SEO Questions G+ community.
Alan Bleiweiss: No. This is called keyword stuffing. Do you really need a title and a caption? And do you need to provide a description that just repeats the words in the title and/or caption? The alternate text attribute is the most important identifier due to needs for visually impaired people. After that, a caption can be helpful sometimes if it`s not obnoxious, or insulting. And a description should really only exist to the side of or below an image and only when it truly provides more value.
Michael Martinez: I usually give the image file a descriptive name because that way I know what it is. Otherwise I`m looking at something stupid like "2324828.gif".
DocMark Palmere: Isn`t SEO ranking effected negatively by empty "alt" tags?
Jey Pandian: I don`t copy my keyword across the board but I do diversify by including entities that have triples such as subject, predicate & object incorporated into complete sentences for blind users. This is important because triples help both search engines and users understand context.
Steve Wiideman: The Google SEO Starter Guide still recommends using descriptive file names.
We saw a slight lift on over 1, 300 URLs when modifying custom store image names to include the keyword and geographical information.
Here`s something else that`s interesting, stock images seem to have less of an impact on rankings, as though Google has already mapped the binary code and cataloged the image based on information it found the first time the image was discovered, and may give less weight to the attributes it finds with each new page it finds the image on.
However, when we create our own image (vector or HD photo), and THEN apply a descriptive name, use a descriptive alt attribute, and use descriptive file properties, we often find the image ranking relatively quickly in Google Images and see overall higher rankings on the pages hosting the unique images.
Users appreciate better images anyway and can tell a stock image from a custom image. Imagine Disneyland using a stock image of a castle instead of a custom image relevant to the season and their target audience.
Who does this well? Bob`s Watches used to take custom photos of each individual product, name it appropriately, and use descriptive alt attributes. Might be something to reverse engineer if they still do it.
Roma Alloui: When saving my images, I use the targeted keyword (long tail if I am targeting that) and a slight variation of synonyms and LSI keyword in title/alt tags with the city/state if that page is targeting a specific geo-location. and Yes, I`ve seen an increased ranking. As far as a caption, I usually don`t use that feature unless it is for an image gallery page.
Neil Cheesman: Re the alt attribute - as from Google - this should be `describing` the image (or if the image is linked - `describing` the destination url) so not sure how the city/state would fit in, unless a location or part thereof is in the image or on the destination page.
Steve Gerencser: Re the stock images. We use them a fair amount but always modify them in some way. Flip, rotate, color shift, crop, s ok merging, anything. If I am going to use a stock image I am going to do.somethimg to it to alter it`s appearance and footprint.