My lord Robert sent along this link to Penn in Hand: Selected Manuscripts in the library of the U of Pennsylvania.
The wonderful aspect is the filters to the collections; you can narrow a search by dozens of settings like date, source, language, illumination (Y/N), as well as the usual bumph about author, title and subject.
Once you pull up an individual item, the first item on the screen is its permanent link! you'll never have to shuffle through the search engine again to find that perfect exemplar! Genius.
When the scanned image of your book of choice is open, you can jump straight to the illuminations! using a dropdown list.
And the zoom option is huge! I can see excellent working detail, like where the gold has rubbed away in a pattern - I think it reflects the brushstrokes of the gesso under it, or possibly even the brushing-on of shell gold in flat gilding. (See pg 29v, Lauds, and use 'full' zoom to look at the initial.)
If I sound excited it's because I've paged through many many a document looking for inspiration - and I probably still will. But finding a search engine that anticipates what I really want to see (the shinies! show me the shinies!) is just a joy.
The only teeny flaw I can find is that there are so many sidebar filters that they force the results down the screen - so at first, I couldn't figure out if my searches were working. So if in doubt, scroll to the bottom of the page.
I can see this becoming my go-to page for new inspirations: quick, precise, and in beautiful detail.