It's been my experience that image ads get flagged very quickly, as it's quite obvious why you're using an image instead of text based ads.

I am, by far, no expert on posting to CL, but I have a lot more luck posting plain text ads, even with a URL in the ad (provided I follow the rest of the tips outlined for getting ads to stick - rotate accounts, only post so many per day, rotate proxy servers, etc).

I use E*asy Ad Pos*ter which outsources the reCa*ptcha automatically and allows you to use "tokens" to vary your ad copy.