Is the love of desiring to look at forbidden images considered an act of worship to them, and is it counted as major shirk, minor shirk, a major sin, or a minor sin that is expiated by good deeds?

Natural love for sin and the psychological inclination towards it is not disbelief (kufr), nor is it considered a deeming of the forbidden as permissible (istihlal). Al-Haytami mentioned that loving what Allah and His Messenger have detested, or the opposite, does not lead to disbelief unless one loves it from the perspective that the Lawgiver detests it, or detests it from the perspective that the Lawgiver loves it. However, if one loves it or detests it for its own sake, without considering that perspective, there is no basis for deeming it disbelief.