I think a leaflet should have 'carpet & upholstery cleaning' in plain site, tell them straight away what the leaflet is about..... then a big picture of you, your van in front of a local landmark.
let them see how old & trustworthy you look, let them see a local familiar landmark so they know you are a local company.
don't try and convert them into wanting their carpets cleaned, aim your message at them that already want it.
this is why you need 10000000s of leaflets putting out you are looking for those persons who want a carpet cleaner