I've been experimenting with some icon packs on my Galaxy S5, and whichever one I use, none of them cover the Gallery icon so I always have an odd one out on my home screen which is annoying! Any advice?
Have you looked thru the icon pack to see if it even includes a gallery icon? Pretty standard so I'd think there would be one. If you're using a custom launcher like Apex or Nova there's an option to change individual icons, you just long press it, select "edit" and then pick what icon you want to use.
Additionally most icon pack designers are open to requests for new designs, so you could try asking for one.