Is there a problem of "chukat goyim" with the bride having "something old, something new, something borrowed, something blue" at her wedding?
As I best understand it, it's an English folk custom/saying.
Please ask your rabbi first, but here's my take on it:
If there's no good reason to do it, I really don't see someone would bother with it.
But if someone (the bride? Or a relative?) really wants it, I can't see the problem. It would mean adopting a non-Jewish custom, but if we follow the Ran's reasoning, that's only a problem if it's origins are pagan, immodest, or totally senseless. Here's what I've read of the custom -- if I'm mistaken, please correct me: It's all about the marriage being new but respecting tradition and needing others' help (or something like that), all of which are nice humanistic themes that don't seem to be pagan, immodest, or senseless. The "something blue" appears to be that Roman brides wore blue, but tracing it further back, it appears this was based on Jewish brides wearing blue (t'chelet)!
How about the bride wearing a garter belt? What I read about this one was that a long time ago, the groomsmen would want an item of the bride's clothing, so they had the bride wear a garter belt, which can be easily removed and given away without causing a wardrobe malfunction. While the "groomsmen taking the bride's clothing" practice is definitely immodest, would you say that the garter belt also has immodest origins? I don't think so.