Your site shows the opposite. Where did you hear differently?

There are things to consider with image ads. You get to show only
one instead of 4. With text ads, you have higher odds of a click.
4 chances instead of 1. That is on ad blocks where 4 text ads will
show.

If you block image ads, you are probably blocking higher paying ads and
less people in the bid pool for your site.

Image ads probably have a much lower CTR than text, but may pay more.

Have 3 ad blocks, have one image/text, the rest text.

But you do have to test. And when I say test, you have to test for at
least 2 weeks. Don't go changing things every hour.

That said, I always say use text only if you are worried.

I almost always put text only on top 2 blocks, image/text on the last one.

If you use less than 3 blocks, most assuredly you should go for all text.

That's my opinion. May not work for your site. Test, test, test.

Paul