How about a curtain track below the window?

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.

Wow - what a view! Yes definitely take the curtains to the ceiling it will add grandeur and frame the view even more beautifully. You can get a custom bent track made that will take the curtains around the corner so the window is not obscured when the curtain are open. Contact your local interior designer - they'll know what to do

You can certainly have different curtains in each room. That way each room will have it's own personality, but the important thing is that they relate to each other in some way. It's good to keep the weight or type of fabric used consistent (maybe they're all linen - but in plain, stripe & pattern). Think - "variation on a theme"