Hi
I had the same issue - not sure if it may be related, seems the icon-theme.cache file was causing all the KDE icons to disappear.
I removed those files from /usr/share/icons and all the icons came back. Also the fallback icon theme seems to work now.
Adding to the ~/.gtkrc-2.0 file
gtk-icon-theme-name = "Tango"
# this file should be placed in your home folder
# and name ".gtkrc-2.0"
#---------------------------------------------------------------
# Section "icon background colors"
#---------------------------------------------------------------
# The following two lines *should* be left uncommented
# if we want the XFCE desktop icon backgrounds to use
# alpha blending (e.g. invisible or some % thereof)
style "xfdesktop-icon-view" {
XfdesktopIconView::label-alpha = 0
#---------------------------------------------------------------
# Section "icon font colors"
#---------------------------------------------------------------
# The next three lines deal with the color of the desktop icon's
# text. You can comment them out if you want you use gtk theme
# colors. Below yields white un-selected normal, green selected,
# and blue when going to another window
#
# I chose three different colors so that you can see the level
# of customization we can do.
fg[NORMAL] = "#ffffff" #this is white
fg[SELECTED] = "#00ff00" # this is green
fg[ACTIVE] = "#0000ff" # this is blue
## my blue fonts to use with nuvola theme & royal blue WM
# environment. a soft shark underbelly blue color if you will.
#fg[NORMAL] = "#528AC6"
#fg[SELECTED] = "#528AC6"
#fg[ACTIVE] = "#528AC6"
}
widget_class "*XfdesktopIconView*" style "xfdesktop-icon-view"
#---------------------------------------------------------------
# Section "xfce panel colors"
#---------------------------------------------------------------
# Use these to change the panel color. Note this should
# be commented out entirely if you decide to use
# Section "xfce panel background" below.
#style "panel"
#{
#this one here is grey
#bg[NORMAL] = "#909599"
# use this with nuvola theme
#bg[NORMAL] = "#64AEE0"
#xthickness = 0
#ythickness = 0
#}
#
#widget_class "*Panel*" style "panel"
#widget "*Panel*" style "panel"
#class "*Panel*" style "panel"
#---------------------------------------------------------------
# Section "xfce panel background"
#---------------------------------------------------------------
style "panel"
{
bg_pixmap[NORMAL] = "Panel/panel-bg.png"
}
# note I simply have a folder in my home called "Panel"
# with the file "panel-bg.png" in it. not sure if you
# can hard code that to somewhere else.
widget_class "*Panel*" style "panel"
widget "*Panel*" style "panel"
class "*Panel*" style "panel"
widget_class "*List*" style "colored"
class "*List*" style "colored"
widget_class "*Text*" style "colored"
class "*Text*" style "colored"
widget_class "*Entry*" style "colored"
class "*Entry*" style "colored"
#---------------------------------------------------------------
# Section "xfce icon fallback theme"
#---------------------------------------------------------------
#
# this is our fallback icon theme in case we launch
# thunar in KDE or XFCE can't find an icon for your theme
# for some icon for some reason.
# a safe default is "Rodent" as it comes with Slackware 12's XFCE
gtk-icon-theme-name = "Tango"
