LXDE does use pcmanfm, correct.
I did some testing, and several pieces were missing after installing the mod package. Check that you have all dependencies installed:
ORBit2 >= 2.14.19
leafpad >= 0.8.18.1
icewm >= 1.3.7
gtkdialog >= 0.8.0
obmixer >= 0.11
aumix >= 2.9.1
yad >= 0.14.0
udisks >= 1.0.2
upower >= 0.9.8
libatasmart >= 0.17
consolekit >= 0.4.3
libgnome-keyring >= 2.32.0
gvfs >= 1.6.6
xarchiver >= 0.5.2
pcmanfm >= 0.9.9
lxterminal >= 0.1.11
lxmenu-data >= 0.1.2
gtkfind >= 1.1
There are also some 32 bit binaries within the package itself, which won't work in Vlocity. One is "fbrun". If you (re)install fluxbox, it will take care of that.
As far as the desktop icons not working:
Pcmanfm-mod does not support the trash function. It is what it is.
The desktop shortcuts have some problems. Try opening the desktop files in a text editor for troubleshooting and corrections. Some have an empty line "Path=". Removing that line helps with pcmanfm. Also, there are call for programs "browser" or "browser-vl", which may not be part of a minimal install. Find the "Exec=****" line, and try that command by itself in a terminal. Problems can be fixed by editing the desktop files to use working commands, or add the needed programs.
Pcmanfm-mod was superseded by Spacefm. That might be a good choice too. This package works for me: http://slackware.org.uk/slacky/slackware64-13.37/desktop/spacefm/0.7.2/spacefm-0.7.2-x86_64-1sl.txz
Switching file/desktop manager will require several changes in the config files. Do a "grep pcmanfm ~/.icewm/*" to find out which ones.
This is a productive thread, keep the ideas coming.