I'm sorry to hear that you're still running into difficulty.
Are you using a custom template? There are some elements of the templates area that are a bit different for custom templates than non custom templates. While we did release a change to the selector so for a standard template, if you select your images prior to adding a template to a listing, the selector will shift to incorporate the number of images you have selected, however, this is not yet the case when using a custom template.
For custom templates you currently need to select the exact number of images to be displayed in your listing and if you've told the selector to use more than you have selected, you would see gray boxes such as you have described. This is currently being looked into by our engineers and we expect to have it resolved in the near future.
If you are not using a custom template and continue to encounter this issue, please file a support case from under the Help tab of the site letting us know a few examples from your Saved Listings where this is occurring and if there are particular templates where you run into this, please let us know which ones and we'll be happy to look into it.