for the unit card, first you need to download Vercingetorix's PAK extractor
from here:
http://www.twcenter.net/downloads/db/?mod=43

then run the PAK extractor (it has instructions) after it's done go to data\packs\DATA\UI\UNITS
it has all nations listed, find the unit card you want and copy and paste it
into data\UI\MERCS & data\UI\SELUCID (you might have to create the folders UI, MERCS & SELUCID)
finally rename it #greek_elephant_armoured

PS- for the photoshop tutorial i have no idea