Allods Online Forum

If you talk about vanity costumes, you can open your wardrobe from the bottom right icon (blue shirt) or press Ctrl + U. There you can pick if you want to view costumes you have "My Costumes" or different categories - to view almost all costumes that you both have and don't have, select "All categories". There are some special costumes that aren't shown in there unless you have them - like one of a kind event stuffs mostly (i.e. community's swimwear contest winner's swimwear design).

If you talk about gears and other items like weapons etc, there's no other way than using the item. There has been some addon but it was meant for vanity costumes before wardrobe was in Allods.