The icons on an iPad allow you to access different features and are displayed as a standard size. People with many icons might prefer them to be smaller so they can view more at once, while people with poor vision may prefer to have larger icons. There is no customisation available, but with standard settings you can use the zoom feature on the iPad to create larger icons. If you jailbreak your iPad, it's possible to have the icons any size you wish.
Changing icon size on a standard iPad
Turn on your iPad and tap the “Settings” icon on the home screen. Select the “General” menu then tap “Accessibility”.
Tap “Zoom” then tap the “Zoom On/Off” button to turn the zoom function on.
Double-tap the screen with three fingers to zoom in. This makes the icons appear larger.
Changing icon size on a jailbroken iPad
Launch the Cydia app and tap “Search” in the bottom right-hand corner of the screen.
Type “Bigify” in the search box. It should return two options -- one in black and one in blue. Tap the black option
Tap “Install” then “Confirm” to confirm the installation. Once it indicates it has finished installing, tap the “Restart SpringBoard” button.
Tap “Settings” and tap the “Bigify” app that now appears in the list.
Find the “Scale Size" and move the slider along to the left to shrink icons or to the right to make them larger. When you feel you have the right size, scroll down and tap “Apply Changes". You'll be able to view the changes once your tablet has reloaded . Tweak the size until you're happy with the results.