It was around 2011 when I first started messing around with Icon Packs. I had a 4th generation iPod Touch and its brand new Retina Display. Everything in that display look sharp as F* and really liked it. That device was where I was introduced to jailbreaking, Cydia and icon theming.
Inside this unofficial IOS Store Cydia was an App called Snowboard (At this point in time I have no idea if this is still a thing because I haven't own an apple device ever since). Anyways, with this app you could download more theming apps that combined with the Snowboard you applied them and it will change your home screen icons. They were really easy to used and modified. Sometimes Devs of the icons will share templates so could create new icons and so everything will stay uniform with proportions and theme colors.
I did my part and soon I started sharing some icons I had created for a theme called IHD2, I think it was the abbreviation for illumination high definition version 2 but not sure. You will create them using photoshop and share them (I don’t think photoshop was the right tool for this).
Later on I purchased an android phone because they were more customizable or so everyone said but BS. I was never able to accomplish this method of easiness I had with IOS. Luckily at that time I found what everybody used back then in Android, the awesome Go Lau