Images can rank in search engines, but it is easier to rank paragraphs of text. There are several reasons:
- Search engines ignore pages that don't have much content on them. Search engine bots can identify text as content reliably. Images are much harder for them to interpret. It is much harder for a bot to know how much content is in an image. It is hard for a bot to see if an image is a content-rich infographic or a content-thin color gradient. As a result, search engines often choose not to index a page with only an image, even if that image has tons of content.
- Paragraphs of text have a lot of different phrases contained in them. There are a lot of possibilities for which to rank. With an image you are limited to ranking for the phrases in the page title and image alt text. There may be a specific phrase you are targeting, but most text pages get a significant portion of their traffic from other phrases.
It isn't impossible to rank a page with only an image, but it makes it much harder than it if it had text too. Conversely, it is also difficult to rank a page with only dense text. Users typically like pages that have both text and images. I wouldn't view it as an either-or proposition, I'd use both text and images if you want to rank well.
If you really want to rank just an image page, use as many of the suggestions as possible from What are the best ways to increase a site's position in Google?