I like rtraincollector's thoughts...
Why not use the gravel area to create a scrapping scene? Grab some derelict, mutilated plastic freight cars from a junker box at the next show. Cut them into logical pieces...roof sections, side panels, end panels, underframe pieces, etc...and then rust/weather the pieces. Maybe even heat-deform a few (bends, crash remnants, etc.) for interest. Then pile them up with a bunch of other scrap metal 'thingies'.
For animation, put a scrapping crew by the pile and embed a torch light from one of the lighting sources (Miniatronics, for example....there are others) Guys with hammers and other tools (Arttista has lots to choose from). Maybe set a job-site compressor (2-wheeler variety, for example...Bowser/Selley has a neat one) with some 'hoses' leading to the work area.
Then, mount a speaker under the table at the scrap site. Consider using one of ITT Products HQ sound modules that complement the scene. I'd recommend considering HQ618-3, Salvage Yard, or any of the series HQ700-703, Track Workers, that have sounds appropriate to the visuals you've created. Or George (ITT) will create a module with the sounds (e.g., mostly welding, torch-cutting) you specifically are looking for at (usually) no additional charge .
Wire the lighting and the sound to an activation button at the table's edge or on your control panel.
There ya go! Inexpensive, lights, sound, ...complementary to the crane. Park a gondola on the side track with a junk load in it. Done.
Well, you wanted an opinion....
FWIW, always....
KD