To take a screen shots:
You must have a controller in port D and you need a memory card with 195 free blocks in slot 2 of that controller.
Now you must choose what type of picture you want, either way you will press 2 buttons on controller D. If you want a closeup of the center of the screen, hold X and press Start; if you want a full screen picture, hold A and press Start. (Note A + X + Start is the same as A + Start) [Thanks to TeleKawaru for the info] The screen will then go black and begin to countdown in the top-left corner, when it hits zero your snapshot will be finished saving on the card in cont. D, slot 2. (Warning: as with all other aspects of PSO, this will NOT pause the game, make sure you're somewhere safe before taking the snapshot.)
You can upload them here:http://pso.donut.dhs.org/