It`s been a while since vanilla RTW for me so I don`t remember exactly if having them unpacked works that well for vanilla units. But, without going to the trouble of unpacking and repacking the pak in which the vanilla unit cards are, you can try this:
1. make a folder named UI in Rome - Total War/data.
2. in this you need to have two folders
\data\UI\UNIT_INFO
\data\UI\UNITS
3. in each of them you need to have a folder with the name of the faction for who`s units you made the cards. For example:
\data\UI\UNIT_INFO\GREEK_CITIES
\data\UI\UNITS\GREEK_CITIES
I think you need to be careful because the mercs have the folder named MERC in Unit_INFO and MERCS in UNITS.
Other then that, the factions have the following names for both folders:
ARMENIA, BRITONS, CARTHAGE, DACIA, EGYPT, GAULS, GERMANS, GREEK_CITIES, MACEDON, NUMIDIA, PARTHIA, PONTUS, ROMANS_BRUTII, ROMANS_JULII, ROMANS_SCIPII, ROMANS_SENATE, SCYTHIA, SELEUCID, SLAVE, SPAIN, THRACE.
4. now, I suppose you have the unit card files in the right format. You need to place the small one in the faction folder from UNITS and the big one in the faction folder from UNIT_INFO.
5. to get the game to use them you need to name them properly. So, you need to use as name what is in export_units(in Rome - Total War/data/text) inside the brackets next to the unit`s name. Example:
Code:
{greek_medium_cavalry} Greek Cavalry
Name both files with that name, but, be sure to make the 2 distinctions:
a. the small one that goes in UNITS needs to have # in front
exemple: #GREEK_MEDIUM_CAVALRY.TGA
b. the bigger one that goes in UNIT_INFO needs to be named with INFO at the end.
example: GREEK_MEDIUM_CAVALRY_INFO.TGA
Hopefully I haven`t forgotten anything.