If a product doesn’t have an image available, you should:
- Submit an image of a similar product
- Wait to submit the product until an image is ready
- Submit a placeholder image with a message, such as “Coming Soon”
- Submit a full color version of your store’s logo
Landing pages with no image or placeholder images that do not show the actual product are not allowed.
Read more here: https://support.google.com/merchants/answer/188494