Stuff of Legends isn't an official resource, nor is the collecting citadel wiki.
GW/Citadel's own catalogues never had the full range. There was stuff that only appeared in one White Dwarf, Citadel Journal. 20 years ago, it wasn't easy to put together a catalogue with Word processing or Desktop Publshing. No PDFs or anything like that back then. Cut and paste was a literally using scissors and glue. Mail orders would very often come back with offers forstuff you never saw elsewhere, on pastel coloured paper foldout sheets.
Not to mention, stuff sometimes was only mail order or only available in shops, seasonal one offs. Even now they still have mail order exclusives, games day specials, limited as part of a big box set etc.
Variations could be prototypes put on sale in limited releases, you know there is a lot of unreleased stuff, and the further back you go the harder it is to keep track. You can be sure to find good resources on everything from 4th edition of warhammer onwards, there's a lot of stuff for 3rd, put the pre-slotta and early slotta stuff often had drawings instead of photos, the first photos were low-res black and white, product numbers have changed for each thing, packaging as well.
You say you're collecting everything for Empire, but you're setting about collecting everything Human, including on top of Empire - Kislev, Norse, Dogs of War (Tileans, Estalians), stuff that pre-dates the current warhammer world setting, that was for D&D and that kind of thing. A lot of the Empire style - the Landsknect look didn't really get locked in as the style until just before 4th ed around 1989-1990. Before that, it's generic fantasy human.
I'd also like to get everything for Empire, which I have mostly got from 4th ed onwards, but I'm not that fussed about stuff from before that wouldn't necessarily fit with the current stuff, unless it's stuff I've still got from when I started, and stuff I always wanted back then, but could never afford or get hold of.
