You are talking here about an E-commerce store so actually you are talking about different kind of grids and list, and if you talk about grids and list then you talk about consistency and uniformity. When people are following a list or grid they expect to find a set of "identical" fields as structure so in the actual list you can not afford to have a picture missing.
Even on the product page, people actually relate a product very much to pictures so again it would be recommended to have a "dummy image" that can be identified clearly as a picture (something like an icon, with or without company logo). The best experience would be to have different dummy pictures for every product category Ex: for a "notebooks" category you should use a washed out simple icon displaying a basic drawn notebook.
And the part with "image not available" is really debatable, at least you should have the image ALT set to "image not available".