Obsessing over heels, thinking about them all the time, spending inordinate amounts of money on them, having all shapes and sizes, becoming aroused by the sight/feel, wearing them at every opportunity, to the exclusion of other items of wardrobe = fetishizing them. Either that, or you're a collector, if there's no sexual component. I think. I'm just an armchair psychologist all the way, yes.
Google sez:
"make (something) the object of a sexual fetish.
"women's bodies are so intensely fetishized"
have an excessive and irrational commitment to or obsession with (something).
"an author who fetishizes privacy""
If you don't slobber over the item in question you're just an avid collector, I suppose. Be careful what you collect though. There was a thread about hobbies at
crossdressers.com and one of the most prolific posters had a collection of thousands of antique nail pullers, I found that amusing somehow.