You can also add a new folder with your file browser and name it example .folder you see the dot before folder and you dont have to name it folder it can be whatever and put pictures in there and they wont show up in gallery
The .dot command doesnt doesnt work with all browsers for me, ive only had it work on Astro File Explorer, I have EStrong file browser and it still see files hidden like this, ".nomedia" method seem to work better for me....
Create a blank txt file on your computer and file>save as ".nomedia" without the quotes. Make sure file type is set to all files. Put that file in any folder on your phone you want to hide. I'm not sure if you can create this file directly on the phone or not. It won't prevent the phone from seeing the folder, it will just hide the files from the default media player or the gallery.