Use alt tag for those images and make certain to include best keyword inside your alt tag.
Use key phrases which are contained in title tag, meta tag and the body text.
Use 2-3 specific key phrases as opposed to the repeating key phrases.
Use plural key phrases in alt tag.
Alt tag shouldn't be lengthy and mustn't exceed a lot more than 7 words.
Don't make irrelevant alt tags which are distantly attached to images rather use key phrases that directly explain the pictures. For instance, if you sell mobile-parts as well as your image shows exactly the same your image title ought to be "mobile-parts.present" rather than "software.present."