Shutters sound like they would be a great addition to your new almost at the beach house. Is it an open concept? If so while you can change things up a bit you'll want to repeat some element and ensure that everything looks great together. Even the rooms you're thinking of putting drapes in might benefit from shutters or wood blinds for both looks and light/privacy control. Also be aware of how these windows will look from the outside. When choosing fabrics look at your existing furniture for inspiration or a piece of existing art or if buying new furniture think about the windows as you do. Everything in the room ties into each other. Ideally you would have swatches and samples of every finish in the room from flooring to window coverings and everything in between including wall colour, area rugs, bedding ect to help make your final decisions easier.

All neutrals so far - you can add any colors. Depends on the look/feel/style you're going after.

Wow! What an incredible view you have! I think you first need to frame it out. I would suggest changing out the carpet with hardwood floors with a worn or weathered look. Definitely get rid of the plastic and replace with white base moulding. Next I would paint the walls a color in the pale grey or grey/blue family. Next, I would suggest some crisp white sheers to frame each window. In the pictures, it looks like the Windows on the right are two windows wide. If so, I would also place panels in the middle of those 2 windows to continue framing the view. These are for decorative purposes only and not intended to distract from the view. It looks like there is a big space between two of the windows. I would locate a large architectural piece to place on that wall to add some interest. Remove all the small items from the window ledges. Finally, I would love a round table in that space. Good luck with your reno!

You are correct the place does and always will look a bit sparse when you only have blinds. The question with curtains is sometimes dependant on what climate you live in and I am not sure where you are so I am going to say. If you need curtains for heat go for a quality curtain to the floor with a fabric that is not stiff (as I discovered I now own after buying curtains off line for my spare rooms). The expensive curtains I brought for my living room have a softer texture and hang so much nicer. As I need Curtains / Roman blinds for heat I have backing fabric etc on the expensive made to measure ones, where as the cheaper ones are just thermals. If you only want to add a curtain for looks and do not require it for heat I would recommend going with a lovely sheer / half see through fabric that drapes really well, this will add a point of interest and you can colour match or add a loved colour to a bare - white on white - cream on cream - colour scheme.