When linking lxappearance 0.5.2 with gtk3 enabled, I get an error saying that I need to add gthread to the linker. The attached patch fixes this problem
I believe this issue is completely fixed in the most recent release of LXAppearance (0.5.6). Try it, please, when it's possible for you and leave a comment if issue wasn't solved to reopen the report. Thank you very much.