A custom wallpaper goes well with custom application icons and custom widgets. It is not particularly difficult to create your own wallpaper. All you need is the Shortcuts app on your iPhone and iPad.
Using the WallCreator shortcut by MacStories, you can create a wallpaper directly on your iPhone or iPad. You can create the wallpaper at random or you can specify a specific color.
WallCreator is incredibly simple to use. It automatically determines which device you are using and creates a wallpaper that is perfect size, so you do not need to know the screen resolution of your iPhone or iPad.
The nice thing is that the shortcut supports both Hex code and simple colors (written with simple English names). So if you want to create a top-down wallpaper in purple and blue, you can do it in seconds.
Once this is done, open the WallCreator shortcut link at Safari (or the default browser of your choice). Then press the "Get Shortcut" button.
The shortcut will now be added to the "My Shortcuts" tab. From here, click the "WallCreator" shortcut to start using it.
Creating a random wallpaper is very simple. For this example, let's create a diagonal slope. Select "Gradient - Diagonal".
Enter the first color name or Hex code and then press the "Done" button.
Then enter the second color name or hex code, and again, press the "Done" button.
Now you will see her preview of wallpaper. Here, click the "Done" button.
If this is your first time using the shortcut, WallCreator will ask for access to photos your. Click the "OK" button to grant the shortcut permission to your images.
Once the wallpaper is saved, press the "OK" button to end it procedure of shortcut.
You can repeat this process to create as many wallpapers as you want.
Once you have created the wallpaper, it's time to put it on your iPhone or iPad.
To do this, open the "Photos" application and go to picture. Here, click the Share button in the lower left corner of the screen.
Now select "Use As Wallpaper".
From the next screen, press the "Set" button.
You can now choose whether you want to set the wallpaper for the lock screen only home screen or both.
And now, the wallpaper is set.
Source of information: howtogeek.com