Could you please specify the exact dimensions of postcard? 5*7 - ?
http://www.printingforless.com/templates/mailing/5x7_Postcards.pdf

I think 5x 7 will work well.

back side empty only stamp and barcode ??

I think we should do plumbing related photos such as a toilet, faucet, water heater and possibly a service van.

Oops - 5 by 7 would work well for the card.

Ok thanks