There must be a lack of image ad sponsors out there when it comes to Google Adsense. I’ve tried running these on two blogs in the past and never once found them relevant to any of my content.
I’m guessing because there are fewer image ad sponsors, diversity suffers. If your content doesn’t match any of the available image ads then you’re just given anything. In my case, I got nothing but online gaming ads with the occasion web host ad or something equally irrelevant.
The default at Google for Adsense is ‘text and image ads’ when setting up your ad block. I had switched to ‘image ads only’ for a few months and found clicks had dropped from their normal rate of ‘rarely’ to ‘never’ for the duration. About a month ago I switched them to ‘text ads only’ and have started to see those pennies rolling in again. (I should be able to retire in the year 2875! )
If you want people to click on ads they must be related to the topic the reader is visiting for. If your blog is about electronics or other popular topics of image ads then you’ll likely do alright with with them. Otherwise, I find ‘text ads only’ is the way to go.
I’m thinking Adsense and similar programs should be thought of as stepping stones anyway. Once your blog reaches a Google Page Rank (PR) of 4 or better there are much better ways to utilize your ad space. I can only hope to achieve such ranking so I can blog about those choices at some point.