The first advertising postcards were introduced in Britain in 1872, and the genre sooned gained popularity as an effective promotional vehicle. Collectors look for cards with distinct and colorful illustrations or photos. While there are many collectors who specialize in the early advertising images or art deco images, collectors also specialize by theme.  Examples include collectors of alcohol,beer or wine cards, household products like soap or food, or services like dentists or doctors.

I recently listed several advertising cards using comic humor to remind doctor/dental patients of appointments.

Advertising Postcard-Dentist-Pink Panther

Advertising Card-Dentist-Family Circus Comics

Another popular topic are roadside attractions.

Advertising Postcard-Roadside Attraction

Advertising Postcard-Roadside Attraction

Another popular topic are gas station and motel/hotel postcards.

Advertising Postcard-Marina/Gas Station

Advertising Postcard-Hotel

And finally, here are advertisements for commercial travel ventures

Advertising Postcard-Rose Bowl Flea Market

Advertising Postcard-Colorado River Cruise