One of the most commonly known Search Engine Optimization (SEO) tips that go around has to do with the way you name and tag the images that you use on your site. Its fairly commonly accepted by most SEO experts that Google not only looks at the text on your blog in order to measure its worth but that Google’s spidering bots also take a look at the code you use in your image files.
Over the years SEO techniques have been developed to abuse this fact and webmasters have ’stuffed’ their ‘alt tags’ with all kinds of keywords - however Google has found ways to combat this and treats such strategies as spamming their bots now - however it is still legitimate to put keywords in you image tags and I would recommend that you do (within reason).
If I’m writing on one of my technical blogs about a product and want to post a picture - I always make sure that the file name of the picture includes the name of the product (with-hyphens-between-words). The system I use (ecto) to publish my blog uploads photos automatically to set the file name as the ‘alt tags’ (which are the words that come up as your picture loads) and uploads the picture to its own URL with the file name in the actual URL. This ensures that when Google’s bot spiders through your site it sees your keywords an additional few times per picture.