From Jim Leonard (trixter -at- oldskool.org)

Here you go.  I made these myself, and made sure to flex all of the 
PCX format's CGA attributes.  These all load perfectly under *REAL* 
PC Paintbrush 4.0 in DOS on a CGA card, so if your decoder screws it 
up, it's the fault of your decoder!

They are:

CGA_FSD.PCX    Standard lightcyan-lightmagenta-white palette (intensity 
bit set) with black background.  When most people think of CGA, they're 
thinking of this.

CGA_TST1.PCX    Different palette (intensite bit NOT set) and different 
background color.  If you can read the text inside the box at the bottom, 
your decoder is shite :-)

CGA_RGBI.PCX    Less commonly-used lightred-lightgreen-yellow palette 
(intensity bit set) with a blue background.

CGA_BW.PCX    640x200 B&W pic in case he didn't have a sample.  
Most PCX decoders handle this just fine.