One of the main reasons android is such a popular operating system is the system wide level of customization that is offered. If you own an android phone or tablet then there seems to be almost no limit to how much or what can be customized. This level customization grows even more when you start to enter the rooted or custom world, with the smallest of details being able to be customization.
While most smaller customization changes will not have a massive esthetic or functional impact, the more of these changes you make, the more of a difference the overall impact of the collective changes results in. That said, there is one small customization that android device owners can employ which does offer a much wider visual difference. These are icon packs. Although, a lot of custom users will already be well versed with icon packs, it is worth providing a quick introduction for those making their way over to android and those making their way over to a new launcher or ROM.
What are they?
Well, in short, an icon pack is an app or add-on which allows the visual changing of how your apps are displayed in your app drawer and on your homescreen. The default look of your apps and icons will depend on what level of android you are using. If using KitKat, then they will look different to those using Lollipop. For those new to customizing, this really is one of the easiest ways in which you can employ a greater visual change to your device with minimal work.
Who can use them?
Anyone can use an icon pack and install them on your device. You do not necessarily need to be rooted or have a custom ROM installed. That said, you generally (for most icon packs) do need to at least have a custom launcher installed. Most icon packs will not be available to those simply running a stock launcher, so you will need to think about installing a custom launcher (to be clear, you don't need to be rooted for a number of launchers). Likewise, if you are rooted and running a custom ROM like CyanogenMod (CM), then chances are you will be able to add an icon pack via the ROM. Likewise, the same is true if you are running Cyanogen OS.
Where are they?
Generally speaking, icon packs are like apps. You can find them anywhere you would expect to find an app. So if you are running a custom launcher then you will be able to easily download and install most icon packs from the likes of the Play Store or the Amazon Appstore. If you are running a custom ROM like CyanogenMod or a custom OS like Cyanogen OS then you will have the added ability to download and install from the inbuilt Theme store.
How do I install them?
This will slightly differ depending on whether you are running a launcher or a ROM. There are simply too many launchers and ROMs to go through one-by-one, so to save some time and make the process clearer, we will quickly look at how to install an icon pack on one of the most popular custom launchers, Nova launcher and one of the most popular customer OSes, Cyanogen OS. It is worth pointing out that subtle difference will exist between different launchers and OSes, but, generally speaking, the logic will be the same.
Installing using Nova
Assuming you already have Nova Launcher installed and running, then you will notice in your app tray there will be a icon dubbed 'Nova Settings'. This is your main hub for Nova and will offer the ability to customize all elements of the launcher, including icons. Open up the settings. Once here, you will see an option mid-way down the screen dubbed "Look and Feel".
Click the tab and on the next screen, you will notice a whole host of icon settings. One of those will be "Icon Theme".
As standard, this will be set to "default". Once you click on the tab, you will see the option to switch between items like "System", "Lollipop" and "KitKat". These are the pre-installed options. However, with the wealth of offerings out there, you can install an almost endless number of Icons.
Now, head over to the Play Store and find your icon pack of choice. If you know what you are looking for then great. If not, this is where the fun begins. Again, there are too many options available and if you search for "icon packs' in Play you will be able to choose between a number of paid and free options available. For this example, we will use Simply 8-Bit Icon Pack. Once you have found what you are looking for, download the icon pack. Most icon packs will not require any 'Special Permissions'.
Once the icon pack has been downloaded. Simply head back to your Nova Settings app and repeat the process of heading towards "Icon Theme". However, on opening this time, you should see the newly downloaded icon pack added to the list.
Click on the icon pack and you are done. At first, you will assume nothing has happened as nothing does immediately happen or open. However, now when you head back to your homescreen, you will see the app icons have all changed to the new style. Repeat the process as much as you want with as many icon packs as you want. You can see the difference between the stock (left) and installed icon pack (right) below.
Installing Using Cyanogen
Now, if you are running CyanogenMod or Cyanogen OS, there is no stopping you from using the above method to install your favorite icon pack. However, one of the benefits of Cyanogen based OSes and ROMs is their own individual method of customization. As such, both the MOD and OS contain a Cyanogen Theme store which makes it much easier to install elements like an icon pack and without the need for an after-market custom launcher. If you have Cyanogen installed on your device, then the Theme store (or Theme Showcase) will already be present in your app drawer. Simply head down to the Theme app and open. Once opened and unlike the Play Store, this store will be full of Theming options. Most will be paid options although there will be a couple of free ones too.
Now, you can search for entire themes by just scrolling down the list and picking the one you want. However, you can also swipe out from the side and click on "Icons" in the side menu and just see the icon packs available.
Once you find the one you want, click on the icon listing to open its main page and click Purchase (even if it is listed as free). For this example we will be using Pressor CM11 Theme.
At this point, you will actually be redirected to the Play Store to where the app resides. Click Install or Purchase and let the icon pack download as normal.
Once downloaded, head back to your main screen, click on your phone settings and you will see a 'Themes' tab.
Click the tab and on the next page you will see an Icons tab.
Click the icons tab and then scroll down to the one you have installed. Click on the icons checkbox and hit apply.
Like on Nova, nothing will immediate happen but once you head back to your home screen or app drawer you will see the changes that have taken effect.