Sure, but I would never buy a full eternity band. The diamonds at the bottom of the ring will take a lot of abuse and will eventually fall out, it is expensive to replace. Also consider the changing of the size, rather than it being 25-50 dollars you will have to add a diamond and that will be really expensive. I would suggest a half or 3/4 anniversary band. It will look like an eternity ring but the diamonds won't go all the way around.

Can you mix diamond shapes, or does it look silly? I found the most perfect thin eternity band that I could wear along with my solitaire & wedding band, but it is done in round, and my solitaire is princess.
thoughts?

My engagement ring has a marque in the middle 3 baguettes on either side of that (6 total) and 4 round on each side of that (8 total) a total of 15 diamonds with 3 different sizes. I want to find a eternity ring in princess cut so I all 4 cuts. My other comment is who cares their DIAMONDS!!!!!! HA HA

I bought a ring, & it is called an eternity band. It has diamonds going all the way around it. It is a size 7, but I wear a size 5. I heard that it can't be sized because of the diamonds that go all the way around it. Is this true? Can't the diamonds be taken out & put back in after it is down sized? Hmmm??? Can anyone give me some ideas?

No, an eternity band cannot be sized. Some jewelers might be willing to "Stretch" a band, which might make it a quarter size bigger, but it cannot be sized down.
The issue isn't about where the diamonds go when you size it down – it's about the structural damage that sizing the ring would cause. To size it down, the jeweler has to change the shape of the ring slightly, which affects the stability of the stone settings – therefore, the ring is unsizeable. Sorry.