There should be no problem with a private IP scheme, so long as:

1. You are using RFC 1918 private IP addresses and not some other range.
2. 10.0.0.0/8 is not recommended for use on the private LAN with U-Verse, as AT&T may be using that range externally for carrier-grade NAT.

Thus, just make sure your range is within 192.168.0.0/16 or 172.16.0.0/12. If you adhere to that, you should not have any problems.