List of valid ip addresses i can change my computers to

You can use any of the addresses listed in this article: http://en.wikipedia.org/wiki/Private_network . Don't attempt to use any other IP address unless your ISP has assigned it to you.

10.0.0.1 > 10.255.255.254

172.16.0.1 > 172.16.255.254

192.168.0.1 > 192.168.255.254

The above does not account for the router address, though these are normally at the low end (e.g. 192.168.0.1 or 192.168.1.1)

Are you talking about your IP address on the internet, or within a LAN?

Ask your ISP for a range of valid IP addresses you can use on the internet, keep in mind your ISP will likely charge you for a static IP. For your LAN, check what the IP address and subnet mask your router has to determine a valid range of IP addresses.