actually... it's not even that. For weapons, sure it's whatever you can equip. However for armor it's your expected armor type, regardless of what you can equip. Also not all cosmetic items are available.
And then there are the items that are restricted for vague reasons that don't make much sense... I've heard some aren't allowed for being 'holiday' items, some for being 'silly' and others are 'available' but their sources are no longer in game so you're fucked.