Centerpieces for rectangle tables

Hi everyone!! I've been googling the heck out if centerpieces and I'm struggling. I'm doing a royal blue, white, and maybe a little silver wedding. We haven't really made up our mind yet on the silver. Wedding is next summer so we have some time for that. We have almost booked our venue though and they only have the rectangle tables. I do not like overly tall centerpieces. Max height for what I think is appropriate is about 15in. I'm not looking for floral arrangements (I'm not a flower person.) How many centerpieces do you put on a rectangle table that can seat between 6 to 8 people? Our reception is going to be light food, so we figure out guests will mostly be socializing and dancing versus paying too much attention to the tables. I've looked into lanterns, but it's hard to tie them into the color scheme without being nautical and that's not us either. Any ideas or suggestions would be great. I'm not sure if our venue allows candles or not at this point as we will be using their linens. I do like the battery operated string lights, but it's also hard to find a good arrangement that would make sense to me.

Thanks!!!