First, let’s discuss a cheaper way to acquire the tower vase. There are always those 20% off your entire purchase from Michael’s in bridal magazines that you could use. Glass vases are typically cheaper at wholesale florist shops as well. See if anyone has any you could borrow (the ones I bought for my wedding have been used in 4 other weddings as of now!). If you know other brides to be and they want to use that type of vase, go in on it together, splitting the costs. You can also rent them, but in this area the way the prices are you might as well buy them and not worry about the hassle.
Second: What can go in the bottom? You can fill the bottom up with a variety of things to add to the centerpiece. Here is a short list of options if you choose: fish gravel, rocks, gems, sand, moss, floralytes, coffee beans, jelly beans, fake water stuff, real water, etc.
Third: How to arrange
The first simple arrange is both cost effective and easy to do. You could use any type of larger flower for this. Just take about 3-4 flowers, place them in the vases so they are on different levels, and then add some grass like plant or you could add stick like accents. Here is one I put together in 1 minute from some flowers laying around.
Second is another easy and cost effective arrangement. Go to the craft store and find a “bunch” of flowers that you like. Example:
Poof them out, place in centerpiece, and then arrange to your liking.
Very little hassle at all. You could add some more flowers or greenery if you want it more filled in. Here is one we did but added two large purple white lilies and some butterflies to it.
Third way to arrange is with a styrofoam ball or a bouquet holder. For the styrofoam ball, use one that is a decent size (this one is too small, but all I could find to show how) 
and that would be soft enough to squoosh onto top of the vase. Use flowers and greenery to cover the ball to achieve the look you are going for. It’s basically the same thing with a bouquet holder, but you just decorate the holder the way you want then just stick it in the vase. Many of the pictures below use that method. You can do that for real or fake flowers. It’s easier to transport that way as well because you can have the vase and top seperate while traveling.
Here are some pictures from flickr of some centerpieces made up.
Last, is to add a tree branch and decorate it to your liking. Here is one with moss in the bottom and a tree branch from my parent’s back yard. I’m going to add origami butterflies, but you could use the feather butterflies, birds, ornaments, jewels, crystals, etc. to decorate it.
Thank you so much!!! I have been searching for some decent pictures and ideas for my white tower vases, and your site is the only place I found some real advise! Totally helped me out!
I feel the same as anonymous…we have been looking for good examples on how to use the eiffel tower vases and yours have been the best by far. We want to use flowers not feathers and now we know what we want to do. Thank you so much!
You are a lifesaver. I knew I wanted these vases, got them and didnot know what to do with them. But thank you a bunch! God Bless!!!