I used to believe that text only worked better than text and image. This was because text ads blend better and they offer more choice to my visitors and more choice makes it more likely that they click. Then an article publishing site I use changed from text only to text and image. They started earning me much bigger click values after this change. I changed the most prominent ad box to text and image on my sites and blogs and I've started earning more from them too. Is this just coincidence or have you noticed something similar?
Google recommends we use Text and Image. I'm also a into text ads. Although Image ads get bigger click values, text ads seems to show to more targeted ads than image ads. This has been my experience so far. Back when I was using Text and Image Ads. I had very good earning per click but the problem was I had low CTR, only when I switched to Text Ads that it increased my CTR. In the end I guess it will depend on your niche.
I've found that 1 click on an image ad can be worth 10 on a text ad. On my own sites I now put the most prominent ad to text and image. The remainder I keep as text only.
usually text ads convert more but it all depends on your site layout, niche, and visit geo/profile. some sites do better with image only ads than text ads. you should experiment with each ad unit for atleast couple of days each to see which one works better for you.
test, test, test.. is the only way to get conclusive results.. Different sites produce different results.
There is image ads only if you use the adsense codes in your adsense account. You can do this by going to Adsense Setup>Get Ads. If you are using blogger and using the adsense widget then there is only Image and Text Ads and Text Ads only.
I'm not sure how many of u guys got the new adsense interface, but I'm testing it right now and what's really cool is that you can see your image ad clicks and earnings compared to your flash ads clicks and earnings compared to text ads. I'm pretty sure nobody who sees his stats will opt out from image ads. In my case image/flash ecpm is about 5 times higher than text ecpm. And I used to believe only text ads work