TRIC is really really good once you get the command switches right!
I will suggest though possibly a more unknown tool
Tomb Raider Custom Screens if you cant get TRIC to do what you want if TRIC doesnt.
A very very basic gui - it definately handles TR4 tr5 pak images etc but I'm also somewhat confident it worked on PCX files too
http://driber.net/homepage/tr/downlo...creens.v20.zip