Put full color Adds in the picture slot!
Instead of the Picture slot for each Yahoo Group, put the adds in that spot instead of having them pop up in the conversations area. This gives them better attention, and everyone realizes that they are NOT spam. Presently, they look like spam, and who wants to buy from a spammer?!
Diane Fahlbusch commented
Since the photo slot is relatively new, and not everyone may be using it, this is the better location to get the attention.