If I have installed LXDE on arch, just using pacman -S lxde, how do I change the theme of the operating system? Do I just get an openbox theme and change that? Pic unrelated.
What do you mean by theme of the operating system? Have you read the wiki page on LXDE?
Read these pages for all the info you need on LXDE. https://wiki.archlinux.org/index.php/LXDE http://wiki.lxde.org/en/Main_Page
From what I can gather on this page http://www.archlinux.org/packages/?q=lxde which lists all the packages that have to do with lxde you'll see one that says lxappearance. Try installing that one with Pacman. You also might be able to find additional themes that you can install somewhere on the internet but I am not willing to do that for you.
I have read both wiki pages. With themes I mean the way the start-menu (to use windows terms) etc looks. All I have found about themes is few links to openbox theme sites so I was wondering if the openbox themes change the way lxde looks because lxde seems to be running on top of openbox.
i do love me a nice wide open box