It sounds like you are referring to looking at your listings on your mobile device after they have posted - however if you see the same issue on a full system it may be that you need to specify the number of images in your listing when selecting a template. We typically recommend setting any template to 24 images to ensure you can use as many as the listing can hold even if you don't intend to use that many images in a listing. There are no detrimental effects if you set the tool to 24 - it won't present blank image spaces when you post if you do not use all 24.
However, if you are referring to viewing active listings on a mobile device, yes using the Optional eBay Gallery images would make more of your images immediately visible, but viewers may also need to tap to see the full description when using mobile devices, where they should see all images in a listing as occurs on a full system.
If you continue to encounter difficulty with this, please feel free to file a support case from under the Help tab of the site letting us know the details of what is occurring for you - please include a sample listing or two by item number or title where the issue is occurring and our support team will take a look into it for you.