Looking at the symbol and terrain use here, I think these could be used to create an illusory city too, or a literal ghost town, perhaps with some additional colour overlay effects, and perhaps some transparency about the symbols (less sure about the latter point, however). Or indeed a city of glass.

While the size may seem wrong, by a strict comparison with some medieval European structures, this isn't for medieval Europe, it's for fantasy D&D, and is close to the scale size for this specific tavern as shown on Mike Schley's map of Saltmarsh in the Ghosts of Saltmarsh scenario book (Wizards of the Coast, 2019), assuming five-foot grid squares here. The appearance isn't quite the same as on that map, but this is an adaptation after all, and although there are a number of designs for the Wicker Goat Tavern online, I don't think there's an official D&D version, so some leeway is to be expected.

In the original adventure (The Sinister Secret of Saltmarsh, TSR's Module U1, from 1981), you were expected to create your own version of the town from scratch - there are a few guidelines for key points, such as Point 4: "Decide where the characters could stay when resting in the town between adventures (the best inn? the only inn?); draw up a tariff (list of expenditures) for their accommodation and food." But that's as close as we got to a description for the inn/tavern, which didn't even get a name back then!

That's not to say such points should just be ignored necessarily, and the heating and access points are useful considerations. However, if the final tavern is meant to fit to the size of the official Saltmarsh map, this is close enough to work for that.

Might be worth tweaking the glow on the lettering to help it stand out more. Might be the colouring instead, but I'm struggling to pick out the numbers for some of the features on the map, and I get the impression the red doesn't seem so clear on the background as the black.

See this blog article by resident CC3+ expert Remy Monsen. Hopefully, that should help, but if you get stuck, feel free to ask here again!

If what you're wanting to do is use online images to make your own vehicle trace-drawings for conversion to symbols, it's worth checking the military museum sites (especially if you're hunting for more obscure vehicles) and also scale model websites - including model kit manufacturers. A number of manufacturers now have PDFs of their kit instructions online that you can freely download, and they sometimes have illustrations showing top-down views for the paint and decal schemes for instance, which might be another starting point.

In terms of constructing the symbols, I'd suggest having a set-up where the lines, base colour, camouflage patterning and any markings are each done as a separate Sheet in CC3+ (or more likely "layers" in non-CC3 graphics programs), to make it easier to swap those for different theatres and times. Also, @Lillhans' comment about separate tank turrets is an excellent one. I'd suggest too using Sheet overlays for the top of various AFVs that have different variants using the same lower chassis and skirts, again to make those easier to swap-out without having to keep redrawing each time.