First up, my personal fave, candles! They add such a romantic ambiance, and the fabric draped ceilings help with this intimate feeling too. (notice the circular seating in 1st image?? Love that!) This is such an inexpensive option compared to flowers!
There are so many options if you decide to use flowers, you can line the aisle, create patterns, you can even create a full on carpet of flower petals!
Lastly here are a few other idea's that can add really pretty effect depending on the style of wedding you have. paper lanterns are fun (just be careful if it's windy venue, you don't want them flying all over the place.) Branches always add a magical forest feel, especially for a winter wedding.
Ribbons are so whimsical and go perfectly with barn farm setting! For a couple who wants glamour, what's better than an aisle lined with mini chandeliers?