I think baloon shades would be too bulkie in the corners. Looks like you have enough room in the corners to get roman shades in there without interfering with each other. How high to mount them would depend on what the drop is. You want the drop to cover up the top of your trim and maybe a bit more. You can get that info from the place you buy from. A nice treatment that would go well with your decor is a vignette by hunter douglas with the cordless option. Beautiful treament with a nice clean look. No cords hanging. If you want to do a cornice in the corner. I would recommended it be done professionaly. Then when you raise the shades they will disappear under the cornice.

I have used SelectBlinds for my current house and my previous house. I LOVE THEM! They send you all the samples you could ever want and the quality has seemed to match the big names window treatments that my mom has in her house. Great customer service too. I contacted them many times about measurements and questions about the product itself. I had one wood valance get slightly damaged in shipping. They sent a replacement - no questions asked. I had the double cell blinds, double cell room darkening, wood blinds and one other room darkening (not a double cell). I wouldn't get the non-double cell again, but only bought them because they were on sale. I would buy all the others again in a heartbeat. If you're really interested I could do some digging to find the exact names of the blinds I have used. Let me know.

We are not window treatment people either, but have started to add some as we've reno'd/decorated a few of the rooms in our house; two bathrooms and our office. They really do help to finish off a room. That said, we're not covering our kitchen bow window, or the DR bow window, though I might consider something for the DR window at some point--just for the window panes themselves, not to cover the whole bow-unit. We used Hunter Douglas' Designer Screen Shades in the Roman Shade style (ours are mounted inside the frames becuase of our window style/frame depth). The shades are very clean-lined and range in sheerness. With the sheerer weaves/fabrics, you can see outside with them down and they allow a lot of light in.

Thanks for all the feedback! In response to some of the comments, the shade is a dark grey and the wall is a lighter grey (Morning Fog by Sherwin-Williams). We had the Silhouette shade professionally measured and installed. The store's interior design consultant recommended the Silhouette and the color for the space (matches our sofa.) Originally, we were thinking a lighter, off-white shade to complement our front door. We also have several Duette Honeycomb shades with an inside mount that were installed by the same store and don't have any issues with gaps. We had a Silhouette shade in a previous home and loved it. However, it was an outside mount for a much larger window. Due to a different issue with the shade, the store will have it replaced. The question is: do we replace it with a Silhouette (and perhaps have the store remeasure the window and see if the headrail can be lengthened by 1/4 to a 1/2 inch, in effect widening the width of the shade to cover all of the glass) or get a Duette honeycomb shade instead? We could also get the shade in a different color which might draw less attention to the side gaps.