are already in the game

copy the kits.big from your cd into you tcm2003 folder
open it with a graphic viewer
These are the numbers for european teams:

241 FC Barcelona
242 Deportivo La Coruna
243 Real Madrid
209 Sk Sturm Graz
245 Ajax Amsterdam
246 Feyenoord Rotterdam
247 PSV Eindhoven
254 SK Rapid Wien
255 VfB Admira Mödling
256 Austria Wien
280 Olympiacos Piräus
298 Rosenborg Trondheim
319 IFK Göteborg
325 Galatasaray Istanbul
448 Athletic Bilbao
449 Betis Sevilla
267 Sparta Prag
44 Inter Mailand
45 Juventus Turin
46 Lazio Rom
47 AC Mailand
50 AC Parma
52 AS Roma
207 GAK
191 SV Salzburg
461 CF Valencia
(there are much more)

then go to your database folder and open the file : OriginalShirtsId.txt

There you have most of the kits:

It starts with
85 --> Numbers of Kits (I think it starts with 65 + number of inserted kits)
1 --> Kit number
Arsenal --> team name

If you want to insert the kits you must insert the number of the Kits --> example :
change number at the top +1
241
Fc Barcelona
Then save and close the file

Open your Game Database editor
Go to your Team (in this case Barcelona)
--> Club --> Kit

And if you done right you must find Fc Barcelona under Original Kits
Choose it
Save it
Violá complete