To be honest, most of my border work is custom done, either relying on old pieces of my own or putting them together on the fly. I do a lot of looking through old maps for inspiration of course. I tend to save a lot of things from Google searches (i think my RightClickSaveAs is such an ingrained habit I don't realize I'm doing it half the time..) for future inspiration as well. And if a site seems to have multiple results that could come in handy in the future, I'll mark it as a favourite.

The ones that aren't, and the ones that are inspired by, usually come from google searches. I don't recall all of the terms I've ever used, but a few good ones are
Border (but you get a lot of modern day maps showing Russia and such)
vector border
antique map
old map
cartouche
ornate

things like that. Adding vector to any search seems to give interesting results too.
Another thing I do a lot of is setting the advanced search options to Large images and Line Art. I just keep rightclicking and open in new tab anything that remotely catches my eye as being useful for what I'm working on right then, until i have between 10 and 15 results. once the results become very few and far between, I keep looking, determined to find just one more (that one more is often the one I end up working with, I find). Though I've also maxed out the search results on more than one occasion - Google won't show more than 1000 results in total, heh.

If you need more specific assistance I'd be happy to, just drop me a PM, though it looks like you've already been directed to one of my typical sources