Tall ceiling, short window: where your windows stop well short of your ceiling (in a barn conversion for instance), we’d recommend Roman blinds. Curtains tend to look odd if they’re not mounted close to the ceiling.
Windows of different sizes and shapes: if you have several windows in one room that sit at different heights or are different sizes, we’d suggest that you either use blinds on all of them or, if that doesn’t suit (say with a long window that calls for curtains), then it’s better to use a curtain on one and a blind on the other, rather than curtains on both. The clear contrast will be more appealing than an awkward near-match.
Bay windows: how you treat a bay depends on whether, when the blinds or curtains are shut, you still want to use the bay. If you do, hang blinds or fit your curtains to curve around the bay (this is where we’d recommend a glider pole – more details on that in part two of this journal). Otherwise, curtains in front work fine, although you may also want blinds so you still have the option of using the bay (like at Christmas, when you might place your tree here).
Unusually shaped windows & skylights: if you have a circular window, for instance, then we might even suggest you go without window treatments at all. It would be a shame to lose the architecture the unusual shape brings. The same goes for skylights. If you do need something though, choose custom-made shutters that fit to – rather than distract from – the shape. That said, curtains also work just fine for arched windows.