IIRC,
pcx is an old format. It was used in retail practically everything including "released" textures. My use of the emote was because pcx indicates the model is (probably) old, maybe made in the early days of Freespace modding.
These days DDS is preferred for textures, because they're compressed and video cards can store them compressed which saves a heap of RAM. Other formats like PNG have to be converted to RGBA pixels (i.e uncompressed) when sent to the video card. So currently it's preferred to use something like PNG for working on & testing textures, but to use DDS for released textures.
FSF is good! I just wish the search was recursive, currently you have to find the right dir for search to find what you're looking for.