That's what my account said when I logged in:
Don't miss out on AdSense image ad revenue
I've had AdSense image ads disabled for ages because it was notoriously off topic and IMO used to hurt my earnings, not help them, as earnings appeared to go up when images when off.
However, now that AdSense isn't paying quite as well as it did last year, I decided to turn it back on when AdSense suggested it and I must admit, earnings appear to be quite a bit stronger for the last few weeks.
Sure, it's showing some off topic stuff but it appears to be paying so what the heck, I'll run it for now and see if the earnings hold up.
I know others have disabled image ads as well so why not give them another try?
What's the worse thing that could happen, lower earnings and you turn it off again?
Worth a shot!