Using small Pinterest chicklet vs. large Pinterest icon

Right now there is no option in the ShareThis Plugin to change the Pinterest button icon size. But you can achieve this after manual installation of ShareThis code. Manual installation can be done after removal of previously installed ShareThis Plugin from WP.
You can refer the link –
https://support.sharethis.com/customer/portal/questions/943449-display-buttons-on-some-pages-but-not-all-pages#sthash.7vnoNk44.dpbs

And then for customizing the buttons icon or adding your own icons, you can refer the below link for ShareThis button customization –
https://support.sharethis.com/customer/portal/articles/446558-custom-buttons