Sometimes I need more information to complete a picture but don't have the budget or time to do an elaborate maquette or huge amounts of research. Kneaded eraser to the rescue! This thing has been stalactites, stalagmites, tombstones, a sci-fi piece of diagnostic tech, and various creatures. By sculpting something basic out of it I can get the angle of view and lighting I want. Other times I've used Sculpey to get a bit more detail.
Here are a few examples of the very helpful kneaded eraser. The plastic cover on the art book acted as a handy substitute for water reflections
I used these "stalagmites" in "Scorpio"
I used this kneaded tombstone in "Voodoo Queen (Woman of Power)"
Like a lot of things, making pictures requires flexibility in thinking and using what's available. To my mind, any tool that has more than one use is money well spent.