Sorry, I didn't phrase my problem very well. I meant that I'm trying to replace the unit icons and have modified Unit_Infocard.tga, but when I start playing a new map I still see the old icons. How do I get my changes into the game?
Try putting your edited file in a mod folder (in a texture folder) enable the mod ... files in the mod folders overide vanila ones.
eg: B5 Mod (folder) - Texture (folder) - Unit_Infocard.tga (modified)
Make sure you've altered the correct Unit_Infocard.tga, there are ones in vanila/Entrench/diplomacy edit the latest AND save it into a mod folder DON'T save it over the vanila ones!