I have a dilema for chair coverings.... All the chairs within the venue are different colors... The table coverings are going to be white burlap with pale yellow runners. My centerpieces are going to be cut aspen trees hollowed out and sunflowers in them. It is a rustic simple wedding.
personally, I wouldn't do anything. the chairs are all the same shape so even though they are different colors they look matching I would rearrange them so that the colors are evenly distributed through the room or use them to color code the tables (eg. blue for the bridal party, white for the brides immediate family, red for the grooms side and yellow for the guests) or you could tie a bow around the chairs to dress them up a little
Maybe you could try draping a swatch of fabric or a wide ribbon over the back of each chair. That might unify them a bit. Maybe you could even tuck a sunflower into the fabric or ribbon somehow onto the back of each chair. Good luck!
OK, you are having a rustic, simple wedding reception. The colors of the chairs fit in just fine with such a decor. Rearrange the chairs so that all chairs at one table are the same color. That will unify things. After that, don't bother covering them up. Covered chairs would fight your theme where as the chairs as they are would complement your theme. The room is very attractive. The ceiling is rustic and beautiful. The room is light and happy. Don't even try to get things too perfect or your rustic theme won't work. Remember that the chair covers and such will only really show before the room is full of guests. As soon as people are mingling you will not even get a full view of the room. Your other table decor sounds perfect. Stop there and consider the table decoration complete. In regard to the general decoration of the venue you are fortunate to have selected a place that will not needs tons of decoration. Depending on the time of day and possible theme you might want to decorate the area near the piano with flowers or other arrangements. The place doesn't need much. I am impressed! Happy wedding!
The backs of the chairs can be wrapped nicely using the rolls of plastic tablecloth that you buy at the hobby shop or party store. You have to have someone with artistic flair to tie beautiful bows using the colors you like and layering them. As for the seats, they won't really matter as much of the time, folks will be sitting in them and you can't see the seats until you sit down. You make bows that drape down the back so you can't see the seat unless you're pulling out the chair to sit down on it. The plastic tablecloth is inexpensive and if you have the right person doing this - it will look like cloth. You could even use floral picks as a part of it.
for my sisters wedding we just went bought some material at walmart and cut them to length and tied them on the chairs and it came out beautiful!!!!