Hello as always it depends on what your setting. If you recent ads set to only contain ads with images and set it to display 10 ads and only say 3 ads out of the last 15 contain images only 3 will show. I hope that explains your problem as this is how the product is coded.
As far as images on the sidebar same thing. It all has to do with how you have it set. If you set the recent ads to contain ads with no images I bet you get a full deck