The first window will never resemble the inspiration photo because of differences in the body and thickness of the fabric used. It may not be possible at this stage to put something behind the fabric to fill It out.

The bay window looks pretty good. I would leave it alone. It is possible to tamper with it and make it worse.

I’d get rid of them and start over.

When you say no horizontal stripe, are you talking about the bottom pleats?

They're two different treatments. The first is called a "London shade" and the second is a "Relaxed Roman with tails".

You should have just enough with the width, but the length needs to be the full length of your window.

I can try to give you a quick tutorial, but I don't have time right now. It would be sometime over the weekend if you can wait.

They'll also need to be lined with a thicker, stiffer lining to help keep it more structured, or it needs a stiffer fabric.

There are a couple issues here. One, the fabric used is quite different from the inspiration photo. Two, the inspiration photo appears to be a functioning window covering that is synched up in order to let the daylight in. What you've attempted is similar to a home with faux shutters that are too small. Perhaps if you approach them as functional and synched (aka. enough fabric to cover the length of the window) you will achieve your look without having to change the fabric.

Good luck!

What others have said above. But a blind like that, unless the fabric is VERY heavy, should have a flannel interlining. It gives the blind so much more body and it hangs much better.

DM When you look at the inspiration photo you can see there is what appears to be a flap (at the very bottom) that has a horizontal stripe on it.

Can anyone give me some advice about the cornice? Why is the fabric wavy? Is the material to thin to put over batting or should it have been put over foam?

Perhaps the "waves" are from where the fabric is pulled taut on the cornice. You are there, is the fabric pulled fairly tight? If that is the issue it goes back to the fact that you are dealing with a thin fabric without substance.

Wrong weight fabric for what you wanted.

I see now. The comments from others are what I would have said. The cornice is wavy for the same reason. The fabric is light and probably pulled unevenly when it was stapled over the batting.You could try using iron on fleece to stabilize and give it more body before reattaching to the cornice.

I'd make it about an inch, no more than 2in. wider than the window, mounted on a 1 x 2 board, so you'd need 1in. returns. If you want to mount it on a bigger board, you'll need to add more for returns. Put 6 inches in each pleat, and I'd put them 6 inches in from each end. I'd use double 1 inch side hems.

If you're making a working shade, I'd make them the full length of the window. If you just want a faux/valance shade, then make them double the size you want them to be, so you have extra folds which gives it the fullness.

I interline everything, but if you don't want to, try to find a napped lining.