Hummm, perhaps CDI could have a "Trends" section...?
Great question! I would say that there is absolutely no problem mixing and matching diamond shapes (or colors!). After all, just think about the many cluster-style rings, brooches and etc – especially from the 30s and 40s – that with spectacular results combine baguettes, emerald cuts, round brilliants, trills and many more in just one jewelry piece... Like anything in fashion, if you tie a look together with a common theme or thread, whether it be materials, colors, textures, or patterns, and most importantly, the fact that you LOVE your pieces, whatever you do should sing. After all, these are accessories and adornments that reflect YOU and YOUR preferences, right? There is no wrong or right here. It is YOUR statement to make.
If you ask me, wearing RB earrings, with a RB tennis bracelet, with a RB solitaire ring is a little TOO safe and staid... mix it up and tantalize the eye with all the beautiful and COMPLEMENTARY shapes, colors and sizes available to you!