You don't need a separate control center for a small network that connects computers in just a few rooms. It's often easier to place the modem and router in one room and run data cables directly to each of the other rooms. You can place the modem and router on your computer table or on a nearby bookshelf.
Leviton and other manufacturers make wall plates that can hold up to six or eight data outlets in the same space as a dual AC outlet. That should be enough for a small network; if you need more, add a second wall plate or replace the first one with a dual-width plate.
When it's time to expand your network, you have two options: You can run new wiring from the original control room to the new location, or you can add a downstream switch in the room closest to the location and run a data cable from there. The second approach can be particularly convenient when the new location shares a wall with a room that already has a data outlet.
Note
It's particularly important to label the wall outlets in a network without a control center. Years from now, when other people try to use your network after you've moved away, they'll need to know where the cable connected to each data outlet goes.
You can also use a small Ethernet switch to use more than one network device in the same room. For example, if there's a data outlet in a teenager's bedroom, you could connect a four-port switch to the wall outlet and connect a computer, a game controller, and an Internet radio to the household network through that switch.