I think I need to see where you are planning to put them I sure think I would want to paint them . I can see how they might work for what you want but be aware they will be moveable and I am not sure that is ideal and to make them stationary loses the uniqueness .

Ok I'm adding a few pics with a sad attempt to add a visual lol to show you ideas where I was thinking. One is as the side wall on the deck (I would probably build a platform on the desk for it. And the other is by itself on the ground level. I have an ac unit that is a bit of an eyesore so I'm tryin to hide it a bit. I do like the colors and plan as of now to keep it but to clean off the rust. I also am adding pics of the backyard in case there is a better location. PS the deck is getting updated and stained here soon so don't judge the decking lol

They're still going to look like factory carts even when repainted and so on - is there no place there were you already have a specific need for storage shelves that can accommodate larger objects?