Open a document with dimensions of 4 by 6 inches in your desktop publishing or graphic design software. Although you don't have to use these dimensions, this is the standard size for a postcard mailer. Yo receive postcard shipping rates from the United States Postal Service, your card must be no larger than 6 by 4.25 inches.
Create the wording use fonts installed on your computer or download free fonts for commercial use. Typography is an important element of gallery cards. Make sure the fonts you select match the tone, mood and color palette of the pieces of art in the exhibition.
Insert pictures of one or more of the pieces of art in the upcoming exhibition. Remember, these photos will be your audience's first impression of the art, so make sure they are high quality. While most gallery cards feature artwork, some are purely typographically based.
Add details about the location, date, time, and works included in the exhibition to the front or back (or both) of the card. Don't forget to leave room for the stamp and mailing address. When the images and text for your gallery card is in place, it can be printed by a professional or at home using blank postcard sheets.