@ellesu
Do they stain it when it's wet, like frescoes on plaster, or after it's dried? (Why would anyone paint concrete floors if there were an alternative that didn't involve lead paint or paint wearing off quickly?)

I wonder if you could put boards down to create a faint imprint before/during staining?

@AlphaCentauri

We had an existing concrete space stained. It had been a carport that we took in after hurricane damage. At that time there were beaucoup techniques and options available depending on how much $$$ you wanted to spend. We were working with insurance settlement $$$ so we went basic. I'd say check around and get and idea what look you want and what you want to spend.