If you don't mind making an amazon purchase, I'd recommend the book 'Scotlands Coast' by Joe Cornish. The photographs are beautiful (he uses a 4x5 view camera), the text insightful and there are maps as to where the photographs were taken :-) There are quite a few images of the islands in the book, but the only thing is that the islands are a bit more difficult to get to in the winter as the ferry timetable is reduced.
Colin Prior also has an excellent book on Scotland, 'Scotland the Wild Places'.
I'd second the people who said Glen Coe, Rannoch Moor and Glen Etive (drop into the Clachaig Inn (go into the 'boot bar') in Glencoe for a pint of Red Cuillin too!), as well as Skye (the Cuilins from Elgol are beautiful at sunset). Skye is the easiest island to get to because it now has a road bridge connecting it to the mainland (drop in and see Ken Bryan at his studio in Broadford if you go to Skye, he's a great guy and would no doubt give you some tips on where to shoot!). These are all my favorite places anyway! Harris is beautiful and there might be the chance of seeing the Aurora Borealis there too... there are some traditional 'Black Houses' on Harris and Lewis that are fun to stay in if you decide to go there! If you go to Harris go to Lewis and see the Callanish standing stones too (I spent my honeymoon on Harris!), but I think you'd be better going to Skye and the Glen Goe/Rannoch moor area.