You have simply found the older description for 1.1. and earlier versions. kko joined Preferences and Advanced Preferences for 1.5. All items are in the old Advanced Pref Panel now.
Location: > Preferences > Top item > First tab from left > down under Skins are 3 checkboxes > the middle one - sorry looked it up in German version & do not know the English words
But it should be the words You quoted.
BTW. 1.5 has the default setting not to show back.bmp. 1.1x shows it by default.
Greetings to Suomi from .De