Sure I can.
Well, the first thing you usually do is to make the image 24-bit (RGB colour).
The next thing is to resize it, so Photoshop can use bilinear filtering for creating the image.
Then you'll have a better image to start from.
Your first job while upgrading them will be to get rid of any colour edges that were in the original V maps. Use the smudge and paintbrush tools as neccessary. Generally it's a good idea to put everything into seperate layers. Don't be surprised if you end up with 100+ layers in your image

See this reference how it should look before and after (when removing colour edges):
Click Now, when this is done, you can start working out and sharpening the little details. Use a mix of layer blending effects, smudge tool, eraser and paintbrush to get it looking as it should. Save your results as TGA images (24-bit) and FS2 will use them over any PCX it finds.
You'll have to add detail / sharpness to it, or you'll end up simply wasting texture memory, as it is now. It would look the same, or better if it was 50% of its current size.