Well . . . it's a figure of speech. Being called on the carpet means 'being rebuked or closely questioned by a person in authority'. But in this case, it just means that someone put an Isetta on a carpet. (Not a good idea if your Isetta leaks as many fluids as my Berkeley does.)
But the folks at FLOR, a manufacturer of carpet tiles decided that a picture of an Isetta parked on a FLOR carpet would look a whole lot more interesting than just a picture of the carpet tiles. (They also have a picture of a Corvette -- but we prefer the bubble car.)
Just another blatent example of exploiting our little cars for commercial gain. But hey, we like it!