These are made from various plastic, resin, and wooden pieces from Games Workshop, Forge World, Armor Cast, a craft store, and various other sources--For example, there is a piece cut off a Star Wars Miniatures Hailfire Droid.
Most of the "bundles" or piles of containers are individual pieces glued together and then glued to a plasticard base. The plasticard was then carefully trimmed to the shape of the footprint or the pieces. However, I originally had the plasticard base cut to rectangles, but I found that to unwieldy in play.
The two large cylinders in the back are wooden rings with 40mm bases glued to the top and bottom.
These tanks are made of pieces from a Pegasus Chem-Plant kit. I wanted some additional stand alone larger container pieces. The one on the left tank is on top of a 25mm GW round base, the middle one is on a medicine bottle cap, and the right one is on a small washer.
They are unique enough to be objective markers, but I intended them for general terrain.
Speaking of objective markers! The bottom row are my Necromunda objective markers. The are assorted resin and plastic bitz from Games Workshop, Forge World, and Armor Cast. They are on 20mm square bases that were simply painted my "Necromunda Terrain Blue".
The top two rows were made by Adeptus-B and we typically use them for "blip" markers, but they can be used for objective markers too! They are numbered 1-8 on the bottom. I flipped one over as an example, but the numbers are yellow, so I'm not sure you can see it.