Architecturefag here, glad you found our help helpful. Looking at your sources, we approve of them all except the first, the fifth, and the last. The first is just too bland, the design is somewhat Greek but that's not too bad, that has its place. The butressing is also a tad excessive, which I didn't think was possible.
The second is decent enough, it's just that those spires are giving me a distinctly asian vibe.
The third, it might just be the perspective but it's far too cartoony. Vertical lines, not diagnols. The windows are good, however.
And for all of these, remember; the rule of cool worked for the catholic church, and it works for 40k. bling it up, yo.