install an icon theme if you want to see
directory icons, lxde-icon-theme is a good one

Then make sure to edit your ~/.gtkrc-2.0 file to 
include this line in the case of the lxde-icon-theme:

gtk-icon-theme-name="nuoveXT2"

That should allow the theme to be used, making pcmanfm 
usable outside of the lxde desktop environment.