I agree that if you can move one, ideally two purposes of the space somewhere else that would be ideal. If you cannot, I would paint the room a lighter grey and all one color--or go white. I am not sure I understand the space completely, but I would start with guitars as your visual interest if this is where they need to stay. Hang them (two or three???) in a row over desk. A thought about the desk. I saw a show once where they made a wood desktop that was thinner. They attached it to the wall in such a way they could unlatch on side from the wall and fold it down. This way you could have more floor space with a chair in front of it for when you needed the desk. Downside is there is no storing anything on desk. Another idea is to have a more narrow desk. West elm makes those kind of narrow tables(parsons). I agree that there the framed photos art are too close together. I like the green curtain with the gray. You might consider painting the storage green(more bright green) with a laquer paint and do a darker gray bedding???? Just try to remember our eyes need "white space" so do not have very much on the walls if you keep the storage and guitars.

Well, doesn't the tile size depend, too, on how big your bathroom is(?). I think my tiler told me once that to use large tiles-- they don't look right unless you can have at least 3 (or 4) complete tiles in a row, either direction. Otherwise, he thinks large tiles don't work well. We used 14" square porcelain tiles in one of our bathrooms, set on the diagonal, with very very narrow grout lines. I really like the look (though I've read here that tiles set on the diagonal are a thing of the past!). Anyway-- I love the tiles on the diagonal, and I think it also makes the room seem bigger. In our other bathroom, we put in penny rounds, which just look like a beautiful mosaic-- really love those-- and no shower (free-standing tub)-- so grout issues just aren't a problem-- stays clean-- we're always barefoot.

And read old house guy: http://www.oldhouseguy.com/windows/ On windows before wholesale replacement with vinyl. The myth out there is that you will save money in the long run on maintenance, etc if buy all new cheap products. It is a sales pitch. Of course a siding guy would tell you your windows/siding/stone are beyond repair. Have you had a mason quote cleaning and repairing the stone?

Good advice already given. Be clear tomorrow when designer comes what your issue is with it, and ask calmly how it can be resolved in the best fashion. It's entirely possible your designer was looking at a photo of it on a tiny screen of some smart phone and wasn't able to clearly even see what the problem was because they didn't have their glasses on or were juggling some other crisis....don't worry. I feel confident they will resolve it...there are loads of solutions none of which should cost you anything other than a few gray hairs :) And I absolutely mean this next comment to be completely helpful: how many other "disasters" have you brought to the designers attention that were really simple fixes or just crossed wires between you and the installers or folks on site? One? Three? Thirty? Be objective and recognize if you, or how you communicate are potentially part of the problem? Some of us get hysterical and hit "send" once too often during a remodel and cause the person on the other end to automatically declare "this is not a problem" to save their sanity and yours....and when there's a real problem like this messy end piece? They have tuned us out from past drama trauma....I speak as a realtor(aka therapist, designer, problem solver, marriage counselor) and as a reformed hysteric who has been on both sides :) Hang tough: and by the way? Love the island and would love to see more photos of your space :) best of luck!