I had the same problem when I switched to kde4 and googled around for an answer. There are several posts on the topic, and most of them include using feh to draw the background (if I remember correctly). I gave up when I tried YASP, a plasmoid that gives you much of the information I wanted conky to give me. Of course, it is not customizable and it doesn't give that wonderful conkish feeling, but it's something.
Still, someone around here will surely provide a real answer.