I use Ubuntu with VNC connection from Windows. I see most of the icons as follows:

System information:
Linux vps568 4.15.0-52-generic #56-Ubuntu SMP Tue Jun 4 22:49:08 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Output of
Code:
xfconf-query -c xsettings -lv
command:
Code:
/Gtk/ButtonImages true
/Gtk/CanChangeAccels false
/Gtk/ColorPalette black:white:gray50:red:purple:blue:light blue:geen:yellow:orange:lavender:brown:goldenrod4:dodger blue:pink:light green:gray10gray30:gray75:gray90
/Gtk/CursorThemeName
/Gtk/CursorThemeSize 0
/Gtk/DecorationLayout menu:minimize,maximize,close
/Gtk/FontName Sans 10
/Gtk/IconSizes
/Gtk/KeyThemeName
/Gtk/MenuBarAccel F10
/Gtk/MenuImages true
/Gtk/MonospaceFontName Monospace 10
/Gtk/ToolbarIconSize 3
/Gtk/ToolbarStyle icons
/Net/CursorBlink true
/Net/CursorBlinkTime 1200
/Net/DndDragThreshold 8
/Net/DoubleClickDistance 5
/Net/DoubleClickTime 400
/Net/EnableEventSounds false
/Net/EnableInputFeedbackSounds false
/Net/IconThemeName elementary-xfce-dark
/Net/SoundThemeName default
/Net/ThemeName Greybird
/Xft/Antialias -1
/Xft/Hinting -1
/Xft/HintStyle hintnone
/Xft/RGBA none
I already tried this command too, but hasn't any visible changes:
Code:
xfdesktop --replace