GeoDirectory does not need images of one exact size. When an image is uploaded, WordPress keeps the original and makes its usual resized copies (thumbnail, medium, large and so on), and GeoDirectory shows the copy that suits each place on the page.

By default the GD > Post Images block or widget uses the medium size and shows images in a 16:9 frame, cropping to fill it. Landscape images close to 16:9, and at least as wide as the largest place you show them, will look best. A full width slider on the details page needs a wider image than a small card in a three column grid.

Change the size or shape shown

Open the GD > Post Images block (or the [gd_post_images] shortcode) in your archive item or details template and use these options:

• Image size: any image size registered on your site, or full for the original upload.
• Aspect ratio: 16by9 (default), 21by9, 4by3, 1by1 (square) or natural, which keeps each image’s own shape.
• Image cover type: whether the image fills the frame by width, height, both, or fits inside it without cropping.

For more on this see How to resize GD post images.

The default image for listings without one

If a listing has no images, GD > Post Images falls back in this order: the listing logo, the category default image, the post type default image, the listing default image, and finally a website screenshot. You set them here:

• Category default image: edit the category and use the Default Listing Image field.
• Post type default image: Places > Settings > General, Default image. Click Show Advanced if you cannot see it.
• Listing default image for the whole site: GeoDirectory > Settings > Design > Archives, Listing default image.