My first suggestion would be to order our Travel Oregon Visitor Guide, Scenic Byways Guide, and Oregon State map that we can mail to you for free. (Here is the link for that.) The scenic byways guide will be able to give you some ideas for beautiful places you might want to photograph, and the state map has little icons that show you where the covered bridges are. This article about the Cottage Grove Covered Bridge Tour Route might be helpful, too.
Some other places might be Cape Perpetua and Thor’s Well, the Samuel H. Boardman State Scenic Corridor, or maybe the Face Rock State Scenic Viewpoint, all on the Oregon Coast. If you are checking out the covered bridges near Cottage Grove there’s a couple of lesser known places with some amazing scenery, like Moon Falls and Pinard Falls, or Koosah and Sahalie Falls.