I started to spend a bit more money and help things come together.
PoE Switch
I found a great deal and ended up buying a 10-port PoE switch.
First, before we get all excited, only 8 of the 10 ports support PoE. Secondly, it is "only" a 10/100 switch, so no gigabit for me. I'm OK with that. The switch was under $60, and I can always upgrade later.
Laying out the Backboard
I started to mount items on my backboard, including the new switch. It took me a long time to figure out where to put the equipment: I wanted enough room to lay it all out neatly and comfortably, but I also want efficiency.
I also want to be able to connect and disconnect items without a lot of effort. And of course I want to be able to see status LEDs without resorting to mirrors or uncomfortable behaviors.
After much trial and error, I found out that the best starting approach is to place all terminating equipment based on the building cabling. One reality of my baseboard is that Coax and Ethernet come from above the baseboard, and I made the choice that electric power will come from the bottom. Everything lays out based on those building cables and how the cables can drape.
Coax and its Splitter
I started with the Coax, as Coax cables are heavy, stiff, and the most difficult to manipulate. My bundle of Ethernet cables is far easier to shape and position.
Considering that coax cables are heavy and stiff, a fairly healthy radius is needed to ease them into position. I have a rather large ~9 port powered coax signal splitter, and all building Coax cables terminate there. I placed the Coax splitter at the top corner of the board in order to ensure that the building coax cables stay as much out of the way as possible. I mounted the splitter so the ports point to the left - that way the cables can come in from the left side of the board, where there is useless space.
Ethernet and its Switch
After the Coax was in place, things started to fall into place. Ethernet was next, and all my building cables were to plug into my new PoE switch. I wanted to be able to see the status lights, and of course I wanted the cabling to be need and tidy.
My PoE switch has mounting holes that are designed to have the ports face up or down. This doesn't work for me, because then I wouldn't be able to see the status lights easily. So I mounted it so the ports face to the right, and then used a screw to captivate the switch onto its mounting screws. As you can see, I have the building ethernet bundle coming down the center of the backboard and into the switch. Given this, the ethernet and the coax do not impeed one another. If I see a bigger switch, I can place a "taller" one in the same position, or I can mount a second one on the right.
Power
Power is easy, it goes on the bottom area of the board. I am starting with a power strip, but I will likely replace it with a mountable UPS in the future. I suspect that a small UPS will be needed, as I plan to minimize power draw of the equipment.
Other Stuff
Now that the fundamentals are on the board, I can start attaching other equipment.
Cable Modem. This goes in the top corner, close to the Coax switch and close to the Ethernet switch.
Router. No router yet, but this will be non-wireless. It will go under the cable modem.
the top center, and power comes from the bottom.