All my image paths were already full urls and not relative. I didn't need Gallery to rewrite anything.
I sure don't remember PP, or Classifieds or RP having ANY impact on the rest of the forum. None of those close my forum (without telling me) and rewrite image paths again without bothering to mention that that is what it is doing.
Is there a way to install Gallery without it attempting to change basic CSS files and forum templates, etc?