I proposed something similar... erm.... bloody hell,
half a decade ago.
In any case, I'm happy to contribute to such a pool. I need to put more paint on most of my NPCs (The Imperial Guard and Warlock, for example), and some of the projects aren't yet finished (e.g. the Sentinel) but I can make models like the Rhino and Wraithguard available.
(Due warning though, it's pretty likely that my Guard and Rhino will appear in my IGT scenario, so if anyone does want to borrow them, it will be dependent on me fudging the GMing order).
For the IGT, while I have no problem with the core concept (it would be daft if everyone who thought they had a good scenario idea for a Rhino had to build their own - we'd either end up missing out on interesting scenarios or end up with an unnecessary number of not quite identical Rhinos), it is at least on a loose level a scored event, so I'd make an insistence that it's made clear when someone has borrowed models for their scenario - it wouldn't be fair to get mistaken credit for work that isn't your own.
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ListRhino:

Wraithguard:
