I tried text ads for a long time and was getting in the range of 10 cents to 70 cents per click, but after some time I thought of changing my strategy and started adding google image ads and was happy with the result.

My suggestion is, have one google image ad per webpage and 2 text ads. One text ad on the top left and above it a google image ad is recommended for good results.

Some websites benefit a lot from google image ads than others. Everything depends on the layout of the website. If the layout is attractive and matches the google image ads then the click thru rates would be high at the same time if the google ads do not match the website then the click thru's would be less.

Most people like to add the google image ads on top, but it is not bad to experiment by adding them at the bottom of the pages too. It is not recommended to add more than one google image ad in a webpage. You can have 2 text links along with one image ad which would get more click thru's. Make sure that you have one google ad on the top left side of the webpage.