What works for me: 1. Rename the image you are using to your keyword. Some people experience better results if they remove hyphens and spaces. eg. yourkeyword.png instead of your-keyword.png 2. Title - Your Keyword 3. Alt - A variation of your keyword eg. 'Your Keyword Is A Good One' 4. Link - If you can link out to a RELEVANT article on a high authority site this will also help. eg. Wikipedia Just Make sure it is a relevant article/post/video to your keyword
Linking to Wikipedia won't really help you out. Make sure the Image description/title and Alt tags contain proper details. If Google indexes the page, it'll give higher priority to the image with these attributes filled in.
the title would be the best description for image, a keyword most probably you can also use it on the alt tag, it will not be an issue if title and alt tag are just the same
Infographic can be a better way to share images plus content. This is more interesting and effective.