After trying several alternatives, it looks like we'll have to use an external image hosting service for images to be displayed in posts (unless you have your own site where you can host images, of course).
photobucket seems to be very popular among Sims fans, and usually works quite well.
Don't put adult-oriented images on photobucket; they'll be deleted. But then, don't put adult-oriented images on Sun Sims, either! Once Sun Sims returns from its shakedown cruise, I'll get a seperate adult board going for the fun stuff.