You could rename your 2 logos. Heres what I did: I renamed the 2 logos princess designed for me to: Apple 1.png (that's Apple, space, 1, dot png) this one had the black fonts. Now the other: Apple 2.png (that's Apple, space, 2, dot png) this one has the white font.
Now, launch iFuntastic, follow directions. When you get to the AT&T Carrier Logo, click Add to List. Locate (in my case) Apple 1.png , select this and click Open. Note: the Apple 2.png file was grayed out and thereforee cannot be selected. This is normal.
Voila! You should see both of the carrier logos. Select them and you're good to go! Thanks to princess for pointing me to the right link when I was having the same issue
Name your file in this manner: xxxxx1.png /xxxxx2.png. I think as long as they end with 1 and 2 you are fine. Or simply name 1.png ang 2.png
The other thing i noticed is that the "original att logo" in ifuntastic is NOT original. Just in case you want to restore your career logo to original don't use that one. That one has shadow beneath and is not as clear as the original logo.