Is remembering "Subhan Allah, Al-Hamdulillah, La Ilaha Illallah, Wallahu Akbar" after lowering one's gaze from immodest girls, with the intention of remembering the Houris and the abiding good deeds, considered an innovation?

Saying that sometimes is permissible, as long as it is not taken as a regular Sunnah (definition) to be consistently observed and its virtue believed in. Forcing it to be like a prescribed litany (wird shar'i) and a regular Sunnah in the designated remembrances is an innovation (bid'ah). Sheikh al-Islam Ibn Taymiyyah says that no one is allowed to innovate for people a type of remembrance or supplication that is not legislated (masnun) and make it a regular act of worship, for this is an innovation in religion that Allah has not permitted, unlike what a person might supplicate with occasionally without making it a Sunnah for people.