Inline images can be advertising. Images you have to fetch manually can be advertising. Text can be advertising. Anywhere you have a means to exchange information, you can also have advertising.
There's a difference between push and pull for images.
If you have to manually click a link to an image, and it's advertising, then there's a loss of trust with the rest of the links on the page.
If the page includes adverts that render automatically, you just say "meh" and try to read the content in a sea of increasingly intrusive and repetitive advertising.
Text advertising is not as successful or intrusive as image advertising.