The code limit is 12 outlets per circuit. Select the appropriate wing nut. The blue has at least three # 12 wires. It doesn't indicate what the maximum is, but 5 or 6 would be OK. Larger sizes may work fine too.
Splicing wires together is called "re-wiring" or "reducing the voltage". Re-wiring means putting all new wires into old holes with new ends on both sides of the box. Reducing the voltage means combining two or more wires into one that carries a lower current. In other words, you can connect as many wires together as will fit into existing holes on the panel. If you want to carry more than the number of circuits specified by code, then you'll need to either replace the panel with one that supports more circuits or add more panels.
Code requires that any hole used for a wire connection be filled with a metal fill plug or cable tie. This ensures that electrical connections are not exposed and allow future maintenance without removing cables from inside the wall cavity.
You can re-wire anywhere in your house. However, do not attempt to take power down stairs or to any area not accessible by an electrician. Also, do not cut corners by using paper tape or string instead of wiring nuts when joining wires together. This type of repair could cause serious damage to your home if made improperly.
There is no limit to the number of lights or receptacles that can be connected to a circuit. However, there is a limit to the number of switches that may be activated at the same time. On a single 15A circuit, you could place 500 receptacles and 500 60-watt lights on 500 switches and still be code compliant. That's 0.5% of your wiring capacity being used by lighting.
As long as one switch controls only one light, you can connect as many items to a circuit as you want. For example, if each room in a house had its own switch, you could plug in lamps and appliances into all of them at the same time without worrying about whether it was too much current for any one item. The only limitation is the total load that the circuit can handle. In other words, don't try to use more power than required by the items that are plugged in!
In most cases, a house will have one main breaker that controls all the circuits feeding into it. If another breaker goes off-line due to a short in one of its plugs or a broken cord, the other lights will still work because they're on separate circuits. You should check with an electrician before connecting multiple loads to one circuit though. It's not recommended unless you know what you're doing!
12 power outlets You may connect 12 outlets protected by a 15-amp breaker using 14-2 wire. For information on the type of plug used in the United States, see Plugs and Plug Types.
These wing wire nut connectors may accept a minimum of three # 12 wires and a maximum of twelve wires residential (home). The actual number of connections that can be made is based on the size of the wirenut connector. For example, if it is an 8-32 thread, then it can hold up to 32 wires.
Wire nuts are used instead of standard electrical connectors because they can be tightened down very securely, making them ideal for holding wires together. They also cannot be connected to anything else except another wire nut or an extension cord plug. However, these advantages come at a price: wire nuts do not provide much room inside them to work with, so depending on how you need to connect your wires you might have to get some other kind of connector too.
In terms of sizing, wire nuts come in several sizes, but the most common ones are 4-40 and 6-50. These numbers refer to the diameter of the hole in the middle of the connector through which the wires pass. A 4-40 wire nut can hold wires as small as 0.5 inches in diameter, while a 6-50 can hold wires as large as 1 inch in diameter. There are also larger wire nuts available for more extensive wiring projects.