I wrote a tutorial on how you can display 8bit PCX files on the PSP screen.
In this tutorial we don't use any other libraries except PSPSDK and basic C libraries.
You will see how you can handle the file with basic C functions and how you can make it ready for the PSP

This tutorial is basically a summary of what I did the last days.
I felt it was important to write a tutorial afterwards as it is really not that complicated.
You don't necessarily have to rely on external libraries

How to load an 8bit PCX image and display it on the PSP
The tutorial and the corresponding files [scr/samplepic] can be downloaded here: