Image ads are exclusive for Adsense for Content pages and not available for Adsense for Search results pages.There are 5 major formats of image ads. The Leaderboard, which is about twice the size of a banner ad, the banner image ad, the skyscraper, the wide skyscraper and the medium rectangle.Google’s technology determines on a tender by tender basis whether image ads, text ads, or a combination of both will make you more money and then delivers the appropriate format.You can choose to run exclusive image ads, but Google recommends selecting both, thereby giving them a better quantity to target the right advertising for your page, generating more revenue for you.Bottom line: taking these two methods together will provide you the best quantity at making the most revenue.

Use Your Blogger Account As Your Image Host
If you want to use your Blogger account as an image host, create a new blog post and upload the image(s) that you want to host on the Blogger server. If you don't want to actually publish the post (you probably won't if you're simply using the post as a way to upload images), you can choose to spend it as a draft instead. The fact that Blogger doesn't provide an option for uploading images outside of creating a blog post indicates that Blogger's intent isn't to have its system used as an image host. However, there are some advantages to using Blogger's setup for hosting images as compared to some of the other free image hosting services. The main advantage, especially for those whose images will be viewed excessively, is that there is no bandwidth limitation.
Change Your Image On Blogger
You can search the Internet for free photos, or go to websites like BigStockPhoto.com or IStockPhoto.com to purchase images. I have found that I do better on the paying sites. I've found a few freebie images to use in the past, but they rattling weren't of the quality that I needed.If you can't find an image that exact size, find one that is slightly bigger and re-size it. Open up your favorite photo application and resize it to the dimension you need.
Now, every you have to do is give the new image the same name as the old image, FTP the new image up to your computer which will replace the old image (select YES if the program asks you do you want to replace the file).Next go to your web browser and refresh the page and you will see the new image. You can repeat this as many times as you want on as many images as you like. That's the quick and easy way to change images on your blog.