If you installed LTspice IV and the update you have a valve library waiting to be used. I will show where it is and how to access it.
Open a new schematic and the component library. Look for valves.
I opened the valve library and select triode.
Place the symbol on the screen.
Place the mouse pointer in the center of the symbol and click to open the dialog box.
Double clicking the box with triode in it turns it blue and displays an arrow.
clicking the arrow calls up a list of available valves. They are grouped. Notice the line above the triode blue bar says End tetrodes........ So scrolling up will show the tetrode list. The triodes will be above them.
Scroll the list and select the valve you want and click OK.
The valve type selected will be displayed on the schematic.
You have a large number of valves available.