All applications' desktop entries can be found in /usr/share/applications.
You can create a desktop entry under ~/.local/share/applications to make your own icon.
zzh@ZZHPC:/usr/share/applications$ sudo cp org.flameshot.Flameshot.desktop ~/.local/share/applications zzh@ZZHPC:/usr/share/applications$ cd ~/.local/share/applications zzh@ZZHPC:~/.local/share/applications$ sudo chown zzh:zzh org.flameshot.Flameshot.desktop zzh@ZZHPC:~/.local/share/applications$ mv org.flameshot.Flameshot.desktop ZFlameshot.desktop zzh@ZZHPC:~/.local/share/applications$ vi ZFlameshot.desktop
Change the 'Exec' line for [Desktop Entry] to "Exec=/usr/bin/flameshot gui --delay 500".
Modify the value of 'Actions' for [Desktop Entry], deleting 'Capture;'.
Delete the [Desktop Action Capture] part.
Delete all the 'Desktop Action' parts, leaving only the [Desktop Entry].
