I like your idea with the curtain. I have some stuff in the garage and even though the garage is competely dry and about 5*C over ambient, everything that's been left out there is covered in stuff. Either green stuff (mold, etc), orange stuff, rust, or white/green boogie snot copper corosion. I had an MCU die out there and when I went to investigate found a spiders egg sack inside it. The whole case was stuffed with white web.
I know throwing a sheet/old curtain over things isn't going to prevent all of that, but I have found that things put under sheets so look a lot better for it!
Another aspect it makes good is sun bleaching. Most of the wires on my DC solar system are pink and grey or just white as they have been sun bleached sitting in the garage window. My headphones in my office, the ear pads are now disintegrated because they got left in the sun in the window. Throwing an old current down the front of the equipment shelves when not in use should help that a lot!