You would have no way of knowing if the image was an ad or part of the article content since they were all served through the same thing. No silly subdomains like ad.domain.com either.
Still quite feasible to detect by size and styling.
I wish web developers had more respect for their audience. If I say, "No ads," I really mean "No ads." Your site is not a special snowflake where I suddenly don't mind seeing advertisements.
I'm also not sure what you mean by "respect for their audience". If I put an ad on a website I didn't ask your opinion and frankly I don't care what you think. Unless you wanna pay my bills. If what you're saying is I should detect the existence of ad block and actually proactively stop writing the code for said ad into the website.....well... that's just silly.