Not many marketers know that this is an option, and most Google image searches have no paid ads. Yet, Google Image Search gets 1 billion page views per day. So:
1) Identify your niche
2) Find the top keyword searches for images in your niche
3) Find an image that will really stand out for those searches
4) Make an ad, get visitors/customers
While you are at it, image search is regularly neglected by SEOs. See if you can get your image at #1.