Perfect – yes that worked. I just changed my global theme to default and clicked “use desktop from theme” on from that which fixed my wallpaper. Then I did what you said – changed my theme back to what I want while avoiding the aspect of the theme that broke it (for me, that was avoiding “use desktop from theme”) and making those changes I like manually instead.
Thanks again! I wouldn’t have been able to boil down the issue to a theme issue if it weren’t for everyone’s help here!