I have the sqlitestudio package installed on FreeBSD 12. It installs the .desktop file, and the matching .svg file. SQLiteStudio is shown in the Applications menu, but the icon only has the exclamation mark, which mean that it wasn't used.

$ pkg info -l sqlitestudio
sqlitestudio-3.2.1_6:
	/usr/local/bin/SQLiteStudio
        ... skip irrelevant files ...
	/usr/local/share/applications/SQLiteStudio.desktop
	/usr/local/share/icons/hicolor/scalable/apps/SQLiteStudio.svg

$ cat /usr/local/share/applications/SQLiteStudio.desktop
[Desktop Entry]
Type=Application
Version=1.0
Name=SQLite database manager
GenericName=Advanced SQLite database manager
Comment=Advanced SQLite database manager
Icon=SQLiteStudio
Exec=SQLiteStudio
Categories=Database;Viewer;DataVisualization;Development;Qt;

$ pkg info | grep xfce
xfce4-appfinder-4.12.0_1       Application launcher and finder
xfce4-calculator-plugin-0.7.0  Simple calculator for the Xfce panel
xfce4-clipman-plugin-1.4.3_1   Clipboard manager for the Xfce panel
xfce4-conf-4.12.1              D-Bus-based configuration storage system
xfce4-cpugraph-plugin-1.1.0    Graphical representation of the CPU load
xfce4-datetime-plugin-0.7.0    Datetime panel plugin for the Xfce desktop
xfce4-desktop-4.12.5           Xfce's desktop manager
xfce4-mixer-4.11.0_4           Volume control for the Xfce desktop
xfce4-mpc-plugin-0.5.1         Musicpd client plugin for the Xfce panel
xfce4-netload-plugin-1.3.1     Network Load plugin for Xfce4
xfce4-notifyd-0.4.4            Visually-appealing notification daemon for Xfce
xfce4-panel-4.12.2             Xfce's panel
xfce4-pulseaudio-plugin-0.4.1_2 Panel plugin for controlling PulseAudio mixer
xfce4-screenshooter-plugin-1.9.5 Application and panel plugin to take screenshots
xfce4-session-4.12.1_6         Xfce's session manager
xfce4-settings-4.12.4_3        Xfce 4 settings application
xfce4-taskmanager-1.2.2_1      Task manager for the Xfce desktop
xfce4-terminal-0.8.8           Terminal emulator for the X windowing system
xfce4-timer-plugin-1.7.0_1     Timer plugin for Xfce
xfce4-tumbler-0.2.6_2          Thumbnail service for Xfce desktop
xfce4-verve-plugin-1.1.1_1     Command line plugin for the Xfce Desktop
xfce4-weather-plugin-0.9.1     Weather plugin for the Xfce panel
xfce4-wm-4.12.5_1              Xfce's window manager