Here's a fun* activity: watch sci-fi and see how many common plumbing fittings, plastic pallet crates, laundry baskets and food containers you can identify. Common in TV and low-budget film, but you would be surprised how much you can find in mega-budget films too (often in the less-prominent parts of scene backgrounds). Note I am not knocking this -- done well, it shows absolute brilliance on the part of the set-designers. Magic may be smoke-and-mirrors, but set-dressing is all about spraypaint-and-lighting! Here is a few good examples...
* for certain values of 'fun' only.
The first Alien movie is a good one for this - check out the devices on the walls inside the ventilation ducts! And much much more!
Such as corridor walls made half (and their floors made wholly) of red plastic shiping pallets. This materal (often spray-painted silver or grey) is a rather stock wall-component of fictional spaceships across the galaxy!
Still with Alien, the highlighted stainless steel plates on the walls and ceiling in the shot below are very popular in a lot of sci-fi. They are heat-exchanger plates out of commercial air-conditioning cooling stacks. I had a dozen of these from a scrap metal merchant several years back - stainless steel sheet is hell to cut, even with an angle-grinder!, which is probably why they are usually used as-is, even though those corner holes always end up making the panels look out-of-place and just-tacked-on (well, to me, anyway - holes that go nowhere for no reason look odd - stick a spray-painted yogurt pot in them or something!).
Here are the same type of panel popping up in Season 4 of the late-70's BBC SciFi Blake's 7
Above: A plate pasted to a grey-painted plywood wall panel austensibly part of a surface-to-ship shuttle, to make it look a bit less like grey-painted plywood! Blakes' 7, Series 4, Episode 11: Orbit. Also featured here, and throughout this series: many hundreds of aluminium/plastic Airline/TV-Dinner food trays glued to walls!
Above: Possibly even the same panel, now part of the wreckage of the crashed spaceship Scorpio Blakes' 7, Series 4, Episode 13: Blake. In this case it could even be sensible: presumably spacecraft have air-conditioning, and hence cooling-stack plates, somewhere inside them!
Above: Ultraworld (a nefarious planet-sized computer) seems to be half-made of the things! Blakes' 7, Series 3, Episode 10: Ultraworld.
The sequel to Alien, Aliens, had a markedly higher budget, but some surprising things still show up if you look hard enough!
Above: Galvanised drain-cover strips: an essential part of any combat-space-ship's armory! Aliens (movie).
I once found out why a certain prop. from Blakes 7 had a metal plate just there when I came across a particular type of vacuum cleaner at the city dump that was a very good fit, right to the hole for the hose where the metal plate was on the prop. No way I would have guessed that was what the prop. was made from otherwise! The vacuum cleaner pictured isn't quite the right model - closest I could WebSearch - but you get the idea. The up-side-down plastic drum, on the other hand... you couldn't get a closer match custom made. Even the ribbing inside the lid matches!
And is that...? Yes, yes it is!! That circuit board between the two hemisperical vacuum-cleaner parts is an Acorn System 1! (With the Acorn logo scrubbed off.) This was the first computer ever sold by early British computer maker Acorn™, who later made the BBC-Micro (based off this board's 2-generations-on successor, the System 3) and then used that to prototype the ARM CPU, which today powers every mobile phone, many SBCs like the Raspberry Pi, and all recent Apple Macs! What a heratage!
Turns out someone else spotted it well before me, but I found it all on my ownsome!
Just for a change, here is my pet peev regarding what almost always looks awful: Plasma balls/plates. It is very rare that I see these things used in SciFi without looking stupid. Below is a grab from Star Trek: First Contact showing the interface where the Borg plug themselves into the collective when not wandering around Borging things. Maybe it is just me, but that plasma plate just looks like what it is -- a kitschy ornament from the 70's. Now I have nothing against plasma plates -- I have one right here on my bookshelf where the books used to be before I digitised them all. But plasma plates, plasma balls and lava lamps are just too familiar as pseudo-techy ornamentation to get away with sticking in a SciFi prop without being visually jarring.
Above 1: The TV series version, despite being (presumably) lower-budget, looks better, to me, since it at least represents something (you can't really see it clearly at TV resolutions, but other content from the era indicates what is showing there is some sort of organo-mechanical circuit diagram). Star Trek TNG, Series 2, Episode 16: Q Who. .... 2: The movie version looks like a green plasma plate as available (at the time) in any electronics-kitsch store, in a variety of colours! Star Trek First Contact (movie). .... And recently, 3: apparently the set designers for Star Trek: Pickard, Series 3, Episode 10: The Last Generation somewhat agreed with me and the lighting on the borg dock has the plasma-plates somewhat obscured behind more TNG-style cyber-organic circuit decals, giving the best of both, I guess.
Which isn't to say you couldn't use plasma plates/balls/etc. But you would have to be very careful of the implementation. For example, using the technique of a plasma-ball to make a long glass tube with electric sparks running down its length would look very effective in some sort of high-power generator or weapon. .... I saw a kids' SciFi many decades ago where a plasma ball was green-screened so you just saw the electric trails and not the glass ball, and that looked really good, despite it being obvious, even at the time to 12-year-old-me, how it was done.