This is one I do on my website....
as shown it is 34.99, but I do it smaller for 29.99, I drop out the lily and rovers, leave in the mixed poms, statice, alstro...
I find that the cubes look like much more when you group like flowers together....so instead of spreading out the stem of lav poms group them all on one side and balance it of with a grouping of staice on the other side or another group of poms, or minis, try doing all one color it does look like more it gives a richer look rather than a chopped up look...I usually use solidago as background filler and let my actual flowers take center stage, people here think that flower is a weed and don't value it when used as a feature...
You cannot get more traditional than my little victorian town that loves nothing more that a teacup loaded with bb and spray roses...yup I sell those....if I can sell them you can too...it's just finding the flowers and style that sells...The grouping thing really works for me....it makes it so there is a whole lot to look at in one area, I think when sitting in the cooler it looks like so much more when peaking all out of one corner is 4 tulips, it makes the customer want to see what other treasure lurk on the other side, where as 4 tulips all around they would see one tulip, a daisy, a piece of green and some fill kind of plain and regular.
The cubes are viewed different than a tall vase....try using the corners of the cubes as the focal areas and then filling in around...hope this helps...