Increase Icon size of af:panelSpringBoard using ADF Skin

ADF Faces af:panelSpringBoard component shows af:showDetailItem in a fancy view using icons as the notation of showDetailItem

From Oracle Docs

The panelSpringboard control can be used to display a group of contents that belongs to a showDetailItem. An icon strip with icons representing the showDetailItem children along with the item's contents are displayed when in strip mode, and a grid of icons with no contents shown is displayed in grid mode. When the user selects an icon while the panelSpringboard is in strip mode, the panelSpringboard discloses the associated showDetailItem. When the user selects an icon while the panelSpringboard is in grid mode, this automatically causes the panelSpringboard to display in strip mode. Typically you would put one or more showDetailItem components inside of the panelSpringboard but you may also alternatively place a facetRef, group, iterator, or switcher inside of the panelSpringboard as long as these wrappers provide showDetailItem components as a result of their execution

I have added a panel springboard on the page and by default, it looks like this

Configure ADF Skin in Jdeveloper 11.1.1.7

In Jdeveloper 11.1.1.7 there is no option to create ADF Skin declaratively
In order to apply skin we have to create a simple CSS file and then configure application to use this CSS file as skin. Jdeveloper doesn't do this for us :( we have to do it manually

So first step is to enable Skin Selectors for ADF Faces, Without enabling this CSS editor doesn't show ADF Faces component tags
CSS files by default supports HTML tags  only

Go to Tools > Preferences > CSS Editor and set CSS level to level 3 and check the box to support ADF Faces Components