Lame_Wolf - 8:54 pm on Nov 18, 2012 (gmt 0)
There is an "image/rich media ads only"
There is no "image only" option on the page where you can edit the ad.
You cannot overtype the options.
I've not tried it, but you may be able to use the old-style code, and overtype the image size - where needed - and have it set to image only.