Reddit mentions: The best biscuits & plugs

If you can do it, trim/sand the hole shiny (top and bottom, inside and out!), prime & paint it. Seal it well! Then use body plug or grommet plug... Bondo would be better, but a waterproof body grommet would work IF you’ve removed all rust and SEALED it well.

Like these.

They come in 1.5” and can be found at car stores, like Napa, O’Reilly’s, AutoZone, etc.

Buy the plug first. Use a metal file and make the hole exactly fit the plug. Then seal it well, let dry, insert plug.

I would cut two of everything to double the thickness. 30° for a full length brace puts the back at about 10" - 10 1/2, something like that - and should be OK if you don't use it for heavy storage or like a workbench or something. Obviously, the critical bit is going to be a good, solid attachment of the braces to the wall.

My only issue would be the material with regard to the braces/brackets. Do you have enough solid wood? I'd just get shelf brackets.

First thing you'll want to do is test the tile shower pan for integrity. To do that you'll need a 2 inch rubber test ball plug or a 2 inch inside pipe expanding test plug. Examples:
https://www.amazon.com/Jones-Stephens-Corporation-T31002-Economy/dp/B000DZGLN2
https://www.amazon.com/Cherne-270024-Test-Ball-2-Inch-Plug/dp/B000VYNU7A
You'll use those to plug the shower drain completely water tight and then fill to the top of the shower curb. Let is sit like that for 24 hours. Check underneath for visible drips and wet spots. The water level should not drop. If it does, even if you don't see leaks, you almost certainly have one. If so there's nothing for it but to break out the tile and start over. Look on the John Bridge forums or the Tile Council of North America for a thorough run down on the correct way for tile shower pans to be constructed.

Like these:

https://www.amazon.com/dp/B000R80OCY/

https://www.amazon.com/dp/B000VYNUD4/

Are you just trying to plug the hole? Get the diameter and google "x inch hole plug" or if you are trying to put cables through it without it cutting into the sheath, then "x inch grommet"

https://www.amazon.com/CAPLUGS-Assorted-Flush-Mount-Furniture/dp/B077R25QQV/ref=sr_1_4?keywords=1-1%2F2+inch+hole+plug&qid=1565888899&s=gateway&sr=8-4

https://www.amazon.com/125-6-150-Rubber-Grommet-Panel-Hole/dp/B01N7IL830/ref=sr_1_6?keywords=1-1%2F2+inch+grommet&qid=1565888996&s=gateway&sr=8-6

https://www.amazon.com/Cherne-270024-Test-Ball-2-Inch-Plug/dp/B000VYNU7A

Nope. Plumber forgot to pull it. Do you have wood floors or it's on a second story?

$10 fix for the faucet.

I'm wondering if you could disassemble the intake and jets, and silicone caulk some of these in.

And then insulate with spray foam?

not nearly as exciting, but you can get cheap plastic caps for short money: https://www.amazon.com/Plastic-Square-Tubing-Caplugs-Package/dp/B008UVD3AU

Not hard, really. I ordered this pack of chipboard, this hole punch, and printed the files out a few different sizes until the hexes fit in the squares. I had a cutting mat and rotary cutter (wife's sewing tools), and also had some super 77 spray adhesive. I sprayed both the chipboard and the paper, glued them on and cut them out.

I bought a 1/2" dowel and cut discs on my table saw for the station tokens but you can buy furniture plugs instead on the cheap. Hole punched the token symbols and glued them on. That's the majority of it. Lots of cutting and patience.

The Cherne 270032 Test-Ball 3-Inch Plug is very handy while trying to figure out a problem with a floor drain.